U.S. patent application number 14/132228 was filed with the patent office on 2014-07-17 for field enhanced separation of hydrocarbon fractions.
This patent application is currently assigned to ExxonMobil Research and Engineering Company. The applicant listed for this patent is ExxonMobil Research and Engineering Company. Invention is credited to Charles Lambert Baker, JR., Michel Daage, Thomas Francis Degan, JR., Gregory J. DeMartin, Ronald M. Gould, X B III, Hyungsik Lee, Philip J. Lenart, Jason M. McMullan, Pawel K. Peczak, Krista Marie Prentice, Anastasios Ioannis Skoulidas, John Stephen Szobota, Lei Zhang.
Application Number | 20140197075 14/132228 |
Document ID | / |
Family ID | 49950091 |
Filed Date | 2014-07-17 |
United States Patent
Application |
20140197075 |
Kind Code |
A1 |
Prentice; Krista Marie ; et
al. |
July 17, 2014 |
FIELD ENHANCED SEPARATION OF HYDROCARBON FRACTIONS
Abstract
Systems and methods are provided for using field enhanced
separations to produce multiple fractions from a petroleum input. A
liquid thermal diffusion and/or electric field separation is used
to produce the fractions. The fractions can then be used to form
multiple outputs that share a first feature while being different
with regard to a second feature. For example, a first fraction from
the plurality of fractions can have a desired value for a first
property such as viscosity index. Two or more additional fractions
from the plurality of fractions can then be blended together to
make a blended fraction or output. The blended fraction can have a
value for the first property that is substantially similar to the
value for the first fraction. However, for a second property, the
first fraction and the blended fraction can have distinct values.
As a result, multiple output fractions can be formed that share a
first feature but differ in a second feature.
Inventors: |
Prentice; Krista Marie;
(Bethlehem, PA) ; Daage; Michel; (Hellertown,
PA) ; McMullan; Jason M.; (Bethlehem, PA) ;
DeMartin; Gregory J.; (Flemington, NJ) ; Szobota;
John Stephen; (Morristown, NJ) ; Gould; Ronald
M.; (Sewell, NJ) ; Skoulidas; Anastasios Ioannis;
(Calgary, CA) ; Lee; Hyungsik; (Fairfax, VA)
; Peczak; Pawel K.; (Basking Ridge, NJ) ; Baker,
JR.; Charles Lambert; (Thornton, PA) ; Degan, JR.;
Thomas Francis; (Moorestown, NJ) ; Zhang; Lei;
(Cherry Hill, NJ) ; III; X B; (Fairfax, VA)
; Lenart; Philip J.; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Research and Engineering Company |
Annandale |
NJ |
US |
|
|
Assignee: |
ExxonMobil Research and Engineering
Company
Annadale
NJ
|
Family ID: |
49950091 |
Appl. No.: |
14/132228 |
Filed: |
December 18, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61753113 |
Jan 16, 2013 |
|
|
|
Current U.S.
Class: |
208/349 ;
196/98 |
Current CPC
Class: |
B03C 2201/02 20130101;
C10G 7/003 20130101; C10G 31/06 20130101; B01D 17/005 20130101;
C10G 71/00 20130101; B03C 11/00 20130101; C10G 53/02 20130101; C10G
32/02 20130101 |
Class at
Publication: |
208/349 ;
196/98 |
International
Class: |
C10G 7/00 20060101
C10G007/00 |
Claims
1. A method for separating a lubricant boiling range feedstock,
comprising: passing a feedstock with an initial boiling point of at
least 200.degree. C. into a gap between a first surface and a
second surface in a thermal diffusion separator; performing thermal
diffusion separation by maintaining the feedstock in the gap with a
temperature differential between the first surface and the second
surface of at least 5.degree. C. for a residence time; withdrawing
a plurality of fractions from the thermal diffusion separator
including a first fraction, a second fraction, and a third
fraction, the first fraction having a first value for a first
property and a second value for a second property; and blending at
least a portion of the second fraction and at least a portion of
the third fraction to form a blended fraction, the blended fraction
having a third value for the first property that differs from the
first value by 2.5% or less and a fourth value for the second
property that differs from the second value by at least 5.0%.
2. The method of claim 1, wherein the plurality of fractions are
withdrawn from the thermal diffusion separator at a plurality of
heights, the second fraction being withdrawn at a height greater
than a height for the first fraction and the third fraction being
withdrawn at a height lower than the height for the first
fraction.
3. The method of claim 1, wherein the first property is viscosity
index, viscosity at 100.degree. C., viscosity at 40.degree. C.,
pour point, cloud point, weight percentage of sulfur, weight
percentage of nitrogen, or weight percentage of aromatics.
4. The method of claim 1, wherein the second property is product
volume, viscosity index, viscosity at 100.degree. C., viscosity at
40.degree. C., pour point, cloud point, oxidation stability,
deposit tendency, Noack volatility, weight percentage of sulfur,
weight percentage of nitrogen, or weight percentage of
aromatics.
5. The method of claim 1, wherein the plurality of fractions
further comprises a fourth fraction, the fourth fraction being
withdrawn from the thermal diffusion separator at a location
between the first fraction and the third fraction.
6. The method of claim 5, wherein the blended fraction is a
non-contiguous blend fraction.
7. The method of claim 1, wherein maintaining the feedstock in the
gap for a residence time comprises flowing feedstock through the
gap in a continuous manner, the residence time corresponding to a
time required for the feedstock to flow across a length of the
gap.
8. The method of claim 1, wherein the feedstock is a lubricant
boiling range feedstock with a T5 boiling point of at least
350.degree. C. and a final boiling point of 600.degree. C. or
less.
9. The method of claim 1, wherein the feedstock is maintained in
the gap in the presence of an electric field.
10. The method of claim 9, wherein the electric field varies
spatially.
11. A method for separating a lubricant boiling range feedstock,
comprising: passing a feedstock with a T5 boiling point of at least
350.degree. C. into a gap between a first surface and a second
surface in a thermal diffusion separator; performing thermal
diffusion separation by maintaining the feedstock in the gap with a
temperature differential between the first surface and the second
surface of at least 5.degree. C. for a residence time; withdrawing
a plurality of fractions from the thermal diffusion separator
including a first fraction, a second fraction, a third fraction,
and a fourth fraction withdrawn from a height between the first
fraction and the third fraction, the first fraction having a first
value for a first property; and blending at least a portion of the
second fraction and at least a portion of the third fraction to
form a blended fraction, the blended fraction excluding at least a
portion of the fourth fraction, the blended fraction having a
second value for the first property that differs from the first
value by 2.5% or less, wherein a yield of product for a combination
of the first fraction plus the blended fraction is greater than a
yield for a contiguous blend of fractions from the plurality of
fractions that has a value for the first property that differs from
the first value by 2.5% or less.
12. The method of claim 11, wherein the first property is viscosity
index, viscosity at 100.degree. C., viscosity at 40.degree. C.,
pour point, cloud point, weight percentage of sulfur, weight
percentage of nitrogen, or weight percentage of aromatics.
13. The method of claim 11, wherein the blended fraction excludes
the fourth fraction.
14. A system for performing hydroprocessing comprising: a
separation volume formed by a first surface and a second surface
aligned to face each other and define a separation volume width of
the separation volume, the separation volume having a separation
volume height defined by a top surface and a bottom surface and a
separation volume length, the separation volume width being from
0.25 mm to 6.0 mm, the separation volume height being at least 0.25
m, and a ratio of the separation volume width to the separation
volume height being less than 500; one or more heating elements
configured to maintain the first surface at a temperature; one or
more first electrodes associated with the first surface and one or
more second electrodes associated with the second surface; an input
manifold in fluid communication with the separation volume; and a
plurality of output channels in fluid communication with the
separation volume, the plurality of output channels being at two or
more different heights relative to the height of the separation
volume.
15. The separation unit of claim 14, wherein the first surface and
the second surface are parallel planar surfaces or wherein the
first surface and the second surface define a closed path.
16. The separation unit of claim 14, further comprising one or more
additional heating elements to maintain the second surface at a
temperature.
17. The separation unit of claim 14, wherein the first surface
comprises a surface of a non-reactive layer in thermal contact with
a bulk material.
18. The separation unit of claim 17, wherein the non-reactive layer
comprises polyethyl ether ketone.
19. The separation unit of claim 14, further comprising at least
one adjustable spacer, the separation volume width being determined
based on a width of the at least one adjustable spacer.
20. The separation unit of claim 14, wherein the plurality of
output channels comprise channels corresponding to at least three
different heights relative to the height of the separation volume.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 61/748,776 filed Jan. 16, 2013 herein
incorporated by reference in its entirety.
FIELD
[0002] This disclosure provides systems and methods for separating
petroleum fractions and other hydrocarbon fractions in the presence
of thermal fields and/or electric fields.
BACKGROUND
[0003] A general problem during petroleum processing is separating
desirable fractions of a petroleum (hydrocarbon) stream from other
fractions that are less desirable or are desirable for a different
purpose. A common example of a separation is to separate a lower
boiling fraction, such as a diesel boiling range fraction, from a
higher boiling fraction, such as a lubricant boiling range
fraction. While separations based on boiling point are well
understood, many desirable qualities in a petroleum fraction are
not directly correlated with boiling point.
[0004] Liquid thermal diffusion provides a method for performing a
liquid separation that is an alternative to boiling point based
separations. U.S. Pat. Nos. 2,541,069 and 3,180,823 are early
examples of using liquid thermal diffusion to separate hydrocarbon
fractions, such as lubricant boiling range fractions. U.S. Pat. No.
3,180,823 also describes use of an additive to facilitate a liquid
thermal diffusion process, and the withdrawal of multiple different
fractions during a separation.
[0005] U.S. Pat. No. 6,783,661 describes a method of using liquid
thermal diffusion for separation of a residue or bottoms fraction
from a process for converting a distillate boiling range feed. The
liquid thermal diffusion is used to separate the bottoms fraction
based on viscosity index. A portion of the bottoms fraction can
then be recycled for further processing.
SUMMARY
[0006] In an embodiment, a method for separating a lubricant
boiling range feedstock is provided. The method includes passing a
feedstock with an initial boiling point of at least 200.degree. C.
into a gap between a first surface and a second surface in a
thermal diffusion separator; performing thermal diffusion
separation by maintaining the feedstock in the gap with a
temperature differential between the first surface and the second
surface of at least 5.degree. C. for a residence time; withdrawing
a plurality of fractions from the thermal diffusion separator
including a first fraction, a second fraction, and a third
fraction, the first fraction having a first value for a first
property and a second value for a second property; and blending at
least a portion of the second fraction and at least a portion of
the third fraction to form a blended fraction, the blended fraction
having a third value for the first property that differs from the
first value by 2.5% or less and a fourth value for the second
property that differs from the second value by at least 5.0%.
[0007] In another embodiment, a method for separating a lubricant
boiling range feedstock is provided. The method includes passing a
feedstock with a T5 boiling point of at least 350.degree. C. into a
gap between a first surface and a second surface in a thermal
diffusion separator; performing thermal diffusion separation by
maintaining the feedstock in the gap with a temperature
differential between the first surface and the second surface of at
least 5.degree. C. for a residence time; withdrawing a plurality of
fractions from the thermal diffusion separator including a first
fraction, a second fraction, a third fraction, and a fourth
fraction withdrawn from a height between the first fraction and the
third fraction, the first fraction having a first value for a first
property; and blending at least a portion of the second fraction
and at least a portion of the third fraction to form a blended
fraction, the blended fraction excluding at least a portion of the
fourth fraction, the blended fraction having a second value for the
first property that differs from the first value by 2.5% or less,
wherein a yield of product for a combination of the first fraction
plus the blended fraction is greater than a yield for a contiguous
blend of fractions from the plurality of fractions that has a value
for the first property that differs from the first value by 2.5% or
less.
[0008] In still another embodiment, a system for performing
hydroprocessing is provided. The system includes a separation
volume formed by a first surface and a second surface aligned to
face each other and define a separation volume width of the
separation volume, the separation volume having a separation volume
height defined by a top surface and a bottom surface and a
separation volume length, the separation volume width being from
0.25 mm to 6.0 mm, the separation volume height being at least 0.25
m, and a ratio of the separation volume width to the separation
volume height being less than 500; one or more heating elements
configured to maintain the first surface at a temperature; one or
more first electrodes associated with the first surface and one or
more second electrodes associated with the second surface; an input
manifold in fluid communication with the separation volume; and a
plurality of output channels in fluid communication with the
separation volume, the plurality of output channels being at two or
more different heights relative to the height of the separation
volume.
[0009] In yet another embodiment, a method for processing a
feedstock is provided. The method includes treating a feedstock
with a T5 boiling point of at least 350.degree. C., the feedstock
comprising a recycled portion, in one or more hydroprocessing
stages under effective hydroprocessing conditions to form a
hydroprocessed effluent; passing at least a portion of the
hydroprocessed effluent into a gap between a first surface and a
second surface in a thermal diffusion separator; performing thermal
diffusion separation by maintaining the at least a portion of the
hydroprocessed effluent in the gap with a temperature differential
between the first surface and the second surface of at least
5.degree. C. for a residence time; withdrawing a plurality of
fractions from the thermal diffusion separator including a first
fraction having a viscosity index of at least 80, a second fraction
having a viscosity index less than the first fraction and less than
90, and a third fraction having a viscosity index less than the
second fraction; and recycling at least a portion of the second
fraction to form the recycled portion.
[0010] In still another embodiment, a method for processing a
feedstock is provided. The method includes treating a feedstock
with a T5 boiling point of at least 350.degree. C. in one or more
first hydroprocessing stages under effective hydroprocessing
conditions to form a first hydroprocessed effluent; passing a first
portion of the first hydroprocessed effluent into a gap between a
first surface and a second surface in a thermal diffusion
separator; performing thermal diffusion separation by maintaining
the first portion of the first hydroprocessed effluent portion in
the gap with a temperature differential between the first surface
and the second surface of at least 5.degree. C. for a residence
time; withdrawing a plurality of fractions from the thermal
diffusion separator including a first separated fraction and a
second separated fraction, the second separated fraction having a
viscosity index of at least 80; and treating a second portion of
the first hydroprocessed effluent and the second separated fraction
in one or more second hydroprocessing stages under second effective
hydroprocessing conditions to form a second hydroprocessed
effluent.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIGS. 1 and 2 schematically show examples of configurations
for performing separations by liquid thermal diffusion.
[0012] FIG. 3 shows parallel planar surfaces with optional features
for reducing the distance between the surfaces.
[0013] FIGS. 4 and 5 schematically show examples of electrode
configurations.
[0014] FIG. 6 schematically shows an example of a configuration for
performing a field enhanced separation.
[0015] FIG. 7 shows separation data from separations performed
using liquid thermal diffusion.
[0016] FIGS. 8 and 9 show separation data from separations
performed using liquid thermal diffusion.
[0017] FIGS. 10 to 14 show various configurations for performing a
field enhanced separation as part of processing of a feedstock.
DETAILED DESCRIPTION
[0018] 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.
Overview
[0019] In various aspects, systems and methods are provided for
using field enhanced separations to produce multiple fractions from
a petroleum input. A liquid thermal diffusion and/or electric field
separation is used to produce the fractions. The fractions can then
be used to form multiple outputs that share a first feature while
being different with regard to a second feature. For example, a
first fraction from the plurality of fractions can have a desired
value for a first property such as viscosity index. Two or more
additional fractions from the plurality of fractions can then be
blended together to make a blended fraction or output. The blended
fraction can have a value for the first property that is
substantially similar to the value for the first fraction. However,
for a second property, the first fraction and the blended fraction
can have distinct values. As a result, multiple output fractions
can be formed that share a first feature but differ in a second
feature.
[0020] Conventionally, petroleum fractions (including feedstock and
partially or fully processed products) have been separated
primarily based on the boiling point of the various compounds.
Boiling point separations can be used to generate a variety of
fractions from a petroleum feed, such as naphtha fractions or
distillate fractions. However, modification of properties within a
boiling range must be achieved by another method, such as by
hydroprocessing or solvent extraction.
[0021] Separations by liquid thermal diffusion provide another
alternative and/or complement to boiling point separations. Instead
of providing a separation based on boiling point, liquid thermal
diffusion results in a separation based on molecular shape and
density that roughly correlates with viscosity index. This
separation can be performed without the use of additional solvents
or other additives. Optionally, a liquid thermal diffusion
separation can be further enhanced by applying a variable electric
field during the separation.
[0022] In various embodiments, combinations of boiling point
separations and liquid thermal diffusion separations can be used a
variety of fractions from a feed, processing intermediate, or
processing product. The ability to perform separations using two
distinct techniques can enable the formation of a variety of
distinct products based on product blending.
[0023] One of the difficulties with using liquid thermal diffusion
or other field enhanced separation methods for separations of
hydrocarbon fractions is achieving a level of throughput that is
commercially useful. Conventional methods of using liquid thermal
diffusion have involved building large separation devices to handle
commercial scale volumes of feed. Unfortunately, such large devices
also involve large residence times for performing a separation
and/or require a large footprint of equipment relative to the
amount of volume passing through the separator. Also, the large
surface areas required for a commercial scale separator result in
high energy consumption and create difficulties in maintaining a
consistent temperature differential between the hot and cold
surfaces of a separator.
[0024] By contrast, a liquid thermal separation according to some
aspects of the disclosure is designed to provide a separation in a
short residence time. This may result in a less complete
separation, but allows for an improved throughput without requiring
addition of additives to the fluid being separated to promote the
separation. The separation can be further enhanced by adding an
electric field, such as a uniform or non-uniform electric field,
across the gap or separation volume of the separator. In some
aspects, increased volumes of a petroleum input stream can be
processed by using a plurality of separation units operating in
parallel mode.
Contiguous, Partially Contiguous, and Non-Contiguous Fractions
[0025] Conventionally, when a product with a specific value for a
property is desired, the product is generated in part by forming
one or more contiguous separation fractions and blending them
together. Contiguous separation fractions represent one or more
fractions that are adjacent and/or contiguous within a given
separation scheme. For example, consider a boiling point separation
where the goal is to form a product with a boiling range of
300.degree. F. (149.degree. C.) to 600.degree. F. (316.degree. C.).
One option for forming this product is to simply form a single
fraction with this desired boiling range. By definition, a single
fraction generated from a separation method, without further
modification, is contiguous with itself. Another option is to form
two separation fractions, such as a fraction from 300.degree. F.
(149.degree. C.) to 400.degree. F. (204.degree. C.), and a second
fraction from 400.degree. F. (204.degree. C.) to 600.degree. F.
(316.degree. C.). Because these fractions represent adjacent
boiling ranges, the fractions are contiguous.
[0026] In still another example, the initial boiling point
separation can result in three fractions. The first fraction has a
boiling range from 300.degree. F. (149.degree. C.) to 400.degree.
F. (204.degree. C.), the second fraction has a boiling range from
400.degree. F. (204.degree. C.) to 550.degree. F. (288.degree. C.),
and the third fraction has a boiling range from 550.degree. F.
(288.degree. C.) to 650.degree. F. (343.degree. C.). In this
situation, in order to blend the fractions to form a product with
the desired range, all of the second fraction is desired, but only
the portion of the third fraction below 600.degree. F. (316.degree.
C.) is desired. The fractions to form the desired boiling range
still represent contiguous fractions, as there is no gap between
the fractions that are blended together with respect to the feature
being used for the separation.
[0027] By contrast, a situation can be considered where the first
fraction with a boiling range from 300.degree. F. (149.degree. C.)
to 400.degree. F. (204.degree. C.) is blended together with the
portion of the third fraction that boils at 600.degree. F.
(316.degree. C.) or less. However, the second fraction that boils
from 400.degree. F. (204.degree. C.) to 550.degree. F. (288.degree.
C.) is not included in the blend. In this situation, the blend is
defined as a non-contiguous blend fraction, since a range of the
separation variable (boiling point) is entirely missing from the
blend.
[0028] Still another option is that the first fraction, the portion
of the third fraction boiling below 600.degree. F. (316.degree.
C.), and an undivided portion of the second fraction are used to
form a blend. In this situation, all of the boiling ranges are
represented in the blend fraction. However, there is less material
present in the blend from the second fraction than would be present
if a separation had been performed to generate a single fraction
with a boiling range 300.degree. F. (149.degree. C.) to 600.degree.
F. (316.degree. C.). This type of blend is defined as a partially
contiguous fraction, since there is not a gap with respect to the
separation variable, but a portion of the expected material is
missing.
[0029] The above definitions were illustrated using temperature
(boiling range) as the variable for separation. For liquid thermal
diffusion, a fraction can be defined as contiguous, partially
contiguous, or non-contiguous based on the VI of the fractions
blended together. Alternatively, many types of liquid thermal
diffusion systems are operated so that the product fractions are
withdrawn based on the height of the separation unit. Another
option for defining contiguous, partially contiguous, or
non-contiguous fractions is based on the withdrawal height of a
fraction from the separation apparatus.
Feedstock and Separation Products
[0030] In the discussion herein, reference will be made to
petroleum, chemical, and/or hydrocarbon feedstocks. With regard to
hydrocarbon feedstocks, unless specifically noted otherwise, it is
understood that hydrocarbon feedstocks include feedstocks
containing levels of impurity atoms typically found in a feedstock
derived from a petroleum mineral source and/or a biological source.
For example, a lubricant boiling range hydrocarbon feedstock could
include several weight percent of sulfur, nitrogen, or oxygen,
depending on whether the feedstock is of biological or mineral
origin as well as the specific source of the feedstock.
[0031] In some alternative aspects, a hydrocarbon feedstock
composed substantially of carbon and hydrogen can be used. In such
alternative aspects, a hydrocarbon feedstock composed substantially
of carbon and hydrogen is defined as a feedstock containing less
than 1 wt % of atoms other than carbon and hydrogen, such as less
than 0.5 wt % and preferably less than 0.1 wt %.
[0032] A wide range of petroleum and chemical feedstocks can be
separated using a field enhanced separation technique, such as
separation via liquid thermal diffusion in the presence of a
thermal field gradient. Some examples of suitable feedstocks
correspond to feedstocks that correspond to distillate boiling
range or heavier materials. Such feedstocks can include, but are
not limited to, atmospheric and vacuum residua, propane deasphalted
residua, e.g., brightstock, cycle oils, FCC tower bottoms, gas
oils, including atmospheric and vacuum gas oils and coker gas oils,
light to heavy distillates including raw virgin distillates,
hydrocrackates, hydrotreated oils, dewaxed oils, slack waxes,
Fischer-Tropsch waxes, oil in was streams, raffinates, other
effluents or fractions of effluents derived from hydroprocessing of
one of the above types of feedstocks, and mixtures of these
materials. In addition, non-conventional feedstocks may be employed
such as bio based feeds or lubricants. Other feeds may include
polymers and/or C.sub.30+ linked molecular streams in order to
isolate key polymers and/or certain shaped linked C.sub.30+
molecules (multiring structures that actually preserve the
viscosity of single rings).
[0033] Some typical feedstocks include, for example, vacuum gas
oils and/or other feedstocks with an initial boiling point of at
least 350.degree. C. (660.degree. F.), such as 371.degree. C.
(700.degree. F.). Alternatively, a feed can be characterized based
on a T5 boiling point. A T5 boiling point refers to the temperature
at which 5 wt % of a feed will boil. Thus, a typical feed can have
a T5 boiling point of at least 350.degree. C., such as at least
371.degree. C. The final boiling point of the feed can be
593.degree. C. (1100.degree. F.) or less, such as 566.degree. C.
(1050.degree. F.) or less. Alternatively, a feed can be
characterized based on a T95 boiling point, which refers to a
temperature where 95 wt % of the feed will boil. In some aspects,
the T95 boiling point of a feed can be 593.degree. C. or less, such
as 566.degree. C. or less. In other aspects, a portion of the feed
can correspond to molecules typically found in vacuum tower
bottoms, so that the upper end of the boiling range for the feed
will be dependent on the source of the feedstock.
[0034] Other typical feedstocks include, for example, feeds with a
broader boiling range, such as feeds that also include distillate
fuel boiling range molecules. Such feedstocks can include molecules
having a boiling range corresponding to vacuum distillation
bottoms, or such heavy molecules may be excluded so that the
heaviest molecules in the feedstock correspond to molecules boiling
in the vacuum gas oil range. For a feedstock including distillate
fuel boiling range molecules, a typical feedstock can have, for
example, an initial boiling point of at least 200.degree. C.
(392.degree. F.), such as at least 225.degree. C. (437.degree. F.)
or at least 250.degree. C. (482.degree. F.). Alternatively, a feed
can be characterized based on a T5 boiling point. A T5 boiling
point refers to the temperature at which 5 wt % of a feed will
boil. Thus, a typical feed can have a T5 boiling point of at least
225.degree. C., such as at least 250.degree. C. or at least
275.degree. C. In aspects where the feed does not include molecules
typically found in vacuum distillation bottoms, the final boiling
point of the feed can be 600.degree. C. or less, such as
593.degree. C. (1100.degree. F.) or less, or 566.degree. C.
(1050.degree. F.) or less, or 538.degree. C. (1000.degree. F.) or
less. Alternatively, the T95 boiling point of the feed can be
593.degree. C. or less, such as 566.degree. C. or less or
538.degree. C. or less. In other aspects, a portion of the feed can
correspond to molecules typically found in vacuum tower bottoms, so
that the upper end of the boiling range for the feed will be
dependent on the source of the feedstock.
Liquid Thermal Diffusion
[0035] FIG. 1 conceptually shows the operation of a liquid thermal
diffusion separator. In FIG. 1, a liquid thermal diffusion
separator includes a hot wall or surface 110 and a cold wall or
surface 120. In this conceptual example, the terms hot and cold
indicate the relative temperatures of surfaces 110 and 120, with
hot surface 110 being at a higher temperature than cold surface
120. The hot surface 110 and cold surface 120, in combination with
a top surface and a bottom surface, define a separation volume or
gap 130. In this example, the length of the separation volume or
gap 130 is not defined, as it corresponds to a dimension
perpendicular to the plane of the page. As an example, cold surface
120 could have a temperature of 150.degree. F. (66.degree. C.)
while the hot surface is at a temperature of 300.degree. F.
(149.degree. C.). The direction of the temperature gradient 142 and
gravitational pull 144 is also shown in FIG. 1. Typically, a liquid
thermal diffusion separator is oriented so that the direction of
gravitational pull is roughly orthogonal to the direction of the
temperature gradient. This allows a separation to be performed
based on molecular shape and density.
[0036] In the conceptual example shown in FIG. 1, a fluid in the
separation volume or gap 130 between surfaces 110 and 120 would
undergo liquid thermal diffusion due to the temperature
differential. Molecules with higher viscosity index values, such as
paraffins, will tend to congregate in the upper portion of gap 130.
Molecules with lower viscosity index values, such as aromatics,
will tend to congregate in the lower portion of gap 130. Two or
more outlets positioned along the vertical direction of the gap 130
can then be used to withdraw fractions with differing viscosity
index values.
Configuration Examples
Hot and Cold Surfaces
[0037] A variety of configurations can potentially be used for the
hot and cold surfaces in a liquid thermal diffusion separator. One
way of characterizing a configuration is whether the separation
volume defined by the hot and cold surfaces corresponds to a closed
path or circuit. Another way of characterizing a configuration is
whether the hot and cold surfaces are separated by a fixed
distance, a distance that varies spatially, or a configuration that
can be adjusted over time so that the separation distance can
change both temporally and spatially.
[0038] FIG. 2 shows an example of a liquid thermal diffusion
separator that has a separation volume in the form of an annular
gap. In FIG. 2, a separator includes an inner cold surface 220 and
an outer hot surface 210. The width for the separation volume
corresponds to the distance between the inner cold surface 220 and
the outer hot surface 210. The separation volume height corresponds
to the height of the annular volume between the cold and hot
surfaces. The separation volume length corresponds to the length
required to traverse the annular volume along a path corresponding
to the midpoint between the outer surface 210 and the inner surface
220. Thus, if a closed loop separation volume corresponds to an
annulus between two right circular cylinders, the separation volume
length will correspond to a circumference of the circle defined by
the midpoint between the outer surface and the inner surface.
Without being bound by any particular theory, FIG. 2 shows an
example of one possible flow mechanism that could result in the
separation observed in a liquid thermal diffusion separator. FIG. 2
shows two separate circulation patterns 238. The circulation
patterns 238 represent the potential movement of higher density
molecules down in the gap and away from the inner cold surface 220,
and the potential movement of lower density molecules upward in the
gap and away from outer hot surface 210. This is one proposed
explanation for how liquid thermal diffusion operates.
[0039] FIG. 2 also includes numbers 1-10, indicating potential
outlet ports or output channels for withdrawing various fractions
from the separator. After a sufficient amount of time, such as the
relaxation time for the separator as will be described below, the
outlet ports can be used to withdraw different types of fractions
from the separator. In the example shown in FIG. 2, a hypothetical
lubricant boiling range feed is considered as the input. Sample
product outputs based on such a hypothetical feed are shown to
illustrate the nature of the separation. The output from a liquid
thermal separation of such a feed can include high VI products such
as wax or Group II/III lubricant base stocks, which are withdrawn
from outlet ports near the top of the separator. At lower output
ports, intermediate VI products such as alkylnaphthalenes and Group
I lubricant base stock can be withdrawn. The lowest ports in the
separator generate low VI products, such as extender oil.
[0040] It is noted that after separation, the resulting product
fractions that can be withdrawn from the output ports may have
different flow properties, such as different viscosities. In a
continuous flow environment, or in any other situation where
withdrawal of the product fractions at comparable rates is
desirable, the relative sizes of the output ports can be selected
to produce similar flow rates. For example, a waxy product that is
withdrawn from an output port near the top of a separator may have
a high viscosity relative to a Group I, Group II, or Group III
basestock product that is withdrawn from a middle or lower portion
of the separator. To compensate for this, output ports with larger
sizes can be used for the ports near the top of the separator in
order to control the flow and/or hydrodynamics of the
separator.
[0041] FIG. 3 shows another example of a configuration for the hot
and cold surfaces. In FIG. 3, hot surface 310 and cold surface 320
correspond to parallel planar surfaces in the form of parallel
plates. FIG. 3 also includes optional protrusions 341 and 342 that
narrow the gap between hot surface 310 and cold surface 320 at a
location. In some aspects, optional protrusions 341 and 342 can be
moved, to change the location between the surfaces where the gap is
narrowed. In such aspects, the protrusions 341 and 342 can move in
tandem, or the protrusions can move independently.
[0042] In a liquid thermal diffusion separator, several geometric
values are relevant for determining the operation of the separator.
These values include the separation volume width of the gap or
separation volume containing the liquid being separated; the height
of the separation volume; and the temperature differential between
the hot and cold surfaces that define the gap or separation volume.
In various aspects, a desirable separation can be performed using a
separator with a smaller than conventional value for the ratio of
separation volume height to separation volume width.
[0043] The separation volume width is defined as the distance
between the hot and cold surfaces in the separator. Typically, the
separation volume width will be in a direction that is orthogonal
or roughly orthogonal to the direction of gravitational force. In
some aspects, liquid thermal diffusion separations are performed in
a separator with a separation volume width of at least 0.25 mm,
such as at least 0.75 mm. Preferably, the separation volume width
can be at least 1.0 mm, such as at least 1.25 mm. In order to
provide an effective separation based on liquid thermal diffusion,
there are practical limits to the width of the gap. As a result,
the separation volume width can be 6.0 mm or less, such as 5.0 mm
or less or 4.0 mm or less. It is noted that the separation volume
width can vary within the gap. For a gap with a variable width, the
separation volume width is defined as the width of the separation
volume based on the full surface area over which the cold surface
faces the hot surface.
[0044] The height of the separation volume is defined as a
dimension that is approximately parallel to the direction of
gravitational force. Additionally or alternately, in some aspects
the separation volume height can be selected to achieve a desired
amount of separation. The separation volume height can be 3.0 m
(3000 mm or 9.8 feet) or less, such as 2.5 m or less, or 2.0 m or
less. The separation volume height can be at least 0.25 m (250 mm),
such as at least 0.4 m or at least 1.0 m or at least 1.5 m.
[0045] Additionally or alternately, in some aspects the ratio of
the separation volume height to the separation volume width is
selected to provide a separation volume height to separation volume
width ratio of 1600 or less, such as 1000 or less or 500 or less.
The ratio of separation volume height to separation volume width
can be at least 50 and preferably at least 100 or at least 200.
Selecting a ratio of separation volume height to separation volume
width defines a balance of factors within a liquid thermal
diffusion separator. Reducing the ratio of separation volume height
to separation volume width limits the amount of feedstock that can
be processed at one time for a given value of the third separation
volume dimension. Reducing the ratio also reduces the amount of
separation. However, the relaxation time required to achieve the
separation is also reduced. By selecting a ratio of separation
volume height to separation volume width that provides a sufficient
degree of separation while also providing a sufficiently low
relaxation time, the throughput for an individual separation device
can be enhanced without requiring an excessive equipment footprint.
By using a plurality of enhanced throughput separation devices, a
commercial scale of feedstock can be processed.
[0046] The remaining dimension of the separation volume, which is
orthogonal to the height and the width, can be referred to as the
length of the gap for convenience. The length of the gap can be any
convenient amount. In order to provide a fixed definition, for a
gap that forms a closed loop (or other closed geometric shape), the
length is defined as distance required to travel the closed loop at
the average midpoint between the hot and cold surfaces. Thus, if a
closed loop separation volume corresponds to an annulus between two
right circular cylinders, the separation volume length will
correspond to a circumference of the circle defined by the midpoint
between the outer surface and the inner surface.
[0047] For a separation volume defined in part by opposing hot and
cold surfaces that do not form a closed geometric shape, any
convenient length for the separation volume can be selected, so
long as a desired level of temperature control can be maintained
over the surface area(s) of the hot and cold surfaces. In some
aspects, the opposing surfaces can be planar surfaces, such as
parallel hot and cold surfaces, or surfaces that angle toward each
other. In other aspects, the opposing surfaces can be defined by a
plane, but at least one surface can have a structural variation
relative to the plane, such as hills and valleys in the surface,
protrusions emerging from the surface, indentations within the
surface, or any other convenient types of features or combinations
of features. Still another option is to have at least one opposing
surface that is defined by multiple planes, so that a portion of
the gap has a first width and another portion of the gap has a
second width.
[0048] The temperature differential between the hot and cold
surfaces can be selected based on a variety of considerations. One
factor is to select a sufficient temperature differential that the
separation by liquid thermal diffusion occurs within a desired time
frame. The greater the temperature differential is between the hot
and cold surfaces, the shorter the relaxation time will be for the
separation to reach separation concentration equilibrium. Another
factor to consider is the characteristics of the liquid being
separated. The cold surface temperature is preferably selected so
that the liquid being separated, including the separated fractions
resulting from the separation, will remain a liquid. If the cold
surface is too cold, a portion of the liquid may crystallize to
form a solid and/or form a glass structure during the separation.
The kinetics of a liquid thermal diffusion are dependent on the
liquid remaining in a fluid state. Thus, formation of a solid or
glass phase is not desirable. For the hot surface, the temperature
is preferably selected so that the liquid being separated,
including the separated fractions resulting from the separation,
does not undergo thermal conversion to form coke or other low value
products. Still another factor for selecting the temperatures is
whether the temperatures can be controlled effectively during a
separation. For example, a cold surface with a temperature near
room temperature may save on energy costs, but the temperature of
such a cold surface may also be difficult to control if there are
temperature swings in the surrounding environment. Having a
temperature for the cold surface that is sufficiently different
from room temperature, such as a temperature of 100.degree. F.
(38.degree. C.) or 149.degree. F. (65.degree. C.), can assist with
maintaining a stable temperature differential between the hot and
cold surfaces.
[0049] In general, the temperature differential between the hot
surface and the cold surface can be from 5.degree. C. to
500.degree. C. From a practical standpoint, a temperature
differential of at least 50.degree. C. is preferable, such as at
least 75.degree. C. or at least 100.degree. C. Having at least a
50.degree. C. (or at least 75.degree. C. or 100.degree. C.)
temperature differential improves the relaxation time required to
achieve equilibrium in a separation. Additionally or alternately,
the temperature differential between the hot surface and the cold
surface can be 300.degree. C. or less, such as 200.degree. C. or
less or 175.degree. C. or less.
[0050] In order to illustrate the benefits of a larger value for
the ratio of separation volume width to separation volume height, a
liquid thermal diffusion separation for a two component system is
described below. The principles of operation for a two component
system are similar to a multi-component system while providing a
more convenient mathematical form.
[0051] In a liquid thermal diffusion separation of a two component
system, the amount of separation that can be achieved is defined by
the equation:
.DELTA. c = 504 L z gL x 4 D T v .alpha. c 0 ( 1 - c 0 ) ( 1 )
##EQU00001##
where .DELTA.c is the concentration difference between the two ends
of a separation volume at steady state, g is the gravitational
constant, L.sub.z is the separation volume height, L.sub.x is the
separation volume width, D.sub.T is the thermal diffusivity, .nu.
is the kinematic viscosity, .alpha. is the thermal expansion
coefficient, and c.sub.0 is the initial concentration of a
component in the two component mixture. As shown in Equation (1),
the amount of separation increases linearly with the height of the
separation volume but decreases based on the separation volume
width to the fourth power. Thus, reducing the ratio of separation
volume height to separation volume width will result in a reduced
amount of separation. However, if the reduced amount of separation
provided at a given ratio of separation volume height to separation
volume width is sufficient, reducing the ratio of separation volume
height to separation volume width has advantages for the relaxation
time t.sub.r required to achieve the separation shown in Equation
(1).
t r = 9 ! ( L z v ) 2 D ( g .pi. .alpha. .DELTA. TL x 3 ) 2 ( 2 )
##EQU00002##
[0052] In Equation (2), D is the molecular diffusivity and .DELTA.T
is the temperature differential between the hot and cold surfaces
in the separator. Here, the relaxation time increases as the square
of the separation volume height and decreases based on the
separation volume width to the sixth power. As shown in Equation
(2), reducing the ratio of separation volume height to separation
volume width will reduce the relaxation time required to achieve
the concentration gradient described by Equation (1).
Electric Field Enhancement
[0053] In order to further improve the relaxation time for a
separator based on liquid thermal diffusion, an electric field can
be used to enhance the rate of separation. In particular, an
electric field that is applied along the width of the separator can
increase the rate of diffusion for molecules within the gap based
on electrophoresis for uniform fields or dielectrophoresis for
non-uniform fields.
[0054] In a typical petroleum feedstock or other hydrocarbon feed,
the vast majority of molecules or particles within the feed will be
neutral and will not have a net charge. If a uniform electric field
is applied to a liquid feed that contains molecules or particles
without a net charge, the uniform electric field will have only a
minimal impact on the diffusion of molecules within the liquid. A
uniform electric field may be effective for aligning molecules with
dipole moments, but no net translational force will be exerted on
the molecules or particles in the liquid.
[0055] By contrast, dielectrophoresis corresponds to diffusion of
molecules in a non-uniform electric field based on the permittivity
(i.e., complex dielectric constant) of the molecules. The electric
field can be a spatially varying electric field, a time varying
electric field, or a combination thereof. In diffusion based on
dielectrophoresis, the electric field will induce a dipole in the
various species contained in a fluid exposed to the electric field.
While such an induced dipole will not result in a translational
force in a uniform electric field, in a non-uniform electric field
the induced dipole can result in a translational force based on the
gradient of the field. In general, species with a permittivity that
is greater than the permittivity of the surrounding medium will
diffuse toward areas of stronger electric field, while species with
a permittivity that is less than the surrounding medium will
diffuse toward areas of weaker electric field.
[0056] Equation 3 shows a general formula for the flux of molecules
(or other species) within a liquid based on various types of
diffusion. In Equation 3, the flux for a molecule or species
J.sub.i (in kg/m.sup.2s) corresponds to a first term based on mass
diffusion (or Brownian motion), a second term based on thermal
diffusion, and a third term based on dielectrophoretic
diffusion.
J i = - .rho. D m , i .gradient. Y i + D T , i .gradient. T T + D E
, i .gradient. ( E 2 ) ( 3 ) ##EQU00003##
[0057] In Equation 3, .rho. is the density of the fluid, D.sub.m,i
is the mass or Brownian motion diffusion constant for species i,
and Y.sub.i is the concentration of species i in the fluid;
D.sub.T,i is the thermal diffusion constant (or thermal
diffusivity) for species i and T is the temperature; and D.sub.E,i
is the electrophoretic diffusion constant for species i, and E is
the electric field. In Equation 3, the first term (corresponding to
Brownian motion) tends to cause mixing of species within the fluid.
By contrast, the second term (corresponding to thermal diffusion)
and the third term (corresponding to dielectrophoresis) tend to
promote separation of species within a fluid. However, based only
on Equation 3, the separation promoted by the second term (thermal
diffusion) is not necessarily aligned with the separation caused by
the third term (dielectrophoresis).
[0058] In a petroleum or hydrocarbon-type feed, paraffinic type
molecules will tend to have smaller induced dipoles while aromatic
molecules will tend to have larger induced dipoles. As a result, a
properly aligned non-uniform electric field can be used to enhance
a liquid thermal diffusion process. A non-uniform electric field
with lower field near the hot wall will tend to enhance the
diffusion of paraffins toward the hot wall. Similarly, a higher
electric field near the cold wall will tend to enhance the
diffusion of aromatics toward the cold wall.
[0059] A variety of potential configurations are available for
providing a non-uniform electric field in the gap between the hot
and cold surfaces of a separator using liquid thermal diffusion.
One option is to simply use an electric field generator that can
generate an oscillating electric field, which results in temporal
field variations. This would allow for generation of a varying
electric field even if the electrodes generating the field were two
parallel plate electrodes. Additionally or alternately, a number of
options are available for generating a spatially varying electric
field.
[0060] One simple example of a spatially varying electric field is
to use a plate electrode on one side of the gap and one or more
point electrodes (or approximately point electrodes, such as rods,
small spheres or hemispheres, or dimples) on the other side of the
gap. FIG. 4 shows an example of the electric field generated from
having a plate electrode on one side of the gap and a point
electrode on the other side. In FIG. 4, lines of constant E field
are shown between the point electrode and the plate electrode.
Instead of using one point electrode, any convenient number of
electrodes with surface area facing the plate can be used. In a
limiting case, a sufficient number of point, rod, small sphere,
etc. electrodes could replicate the effects of a plate electrode,
resulting in little or no spatial variance in the electric field.
However, as long as the width of the gap is not substantially
larger than the spacing between electrodes (such as 50 times larger
or 100 times larger), using a plurality of point electrodes will
result in a spatially varying electric field with gradients that
can induce dielectrophoretic diffusion. Still other combinations of
point source electrodes, (or approximate point sources), small
plate electrodes with distances between the plates, and or
protruding electrodes can be used.
[0061] FIG. 5 shows an example of a point, rod, small sphere, or
dimple electrode configuration that can be used to enhance a liquid
thermal diffusion separation. The example shown in FIG. 5
represents only one of two electrodes. The opposing surface can
have any convenient type of electrode, such as a plate electrode.
The example shown in FIG. 5 uses a plurality of point (or
approximately point) electrodes to form a triangular shape. The
descending hypotenuse of the triangle results in an electric field
gradient that can assist molecules with larger induced dipole
moments in traveling to the bottom of the separator.
Separation Products
[0062] A field enhanced separation can be used to generate a
plurality of products, and preferably at least three products, from
an input feed to a separator. Similar to a fractionator, the
plurality of products can be withdrawn from a liquid thermal
diffusion separator at various heights. The number of different
products withdrawn from a separator can depend on the types of
desired products and the nature of the input feed to the
separator.
[0063] In an aspect where a general separation of a lubricant
boiling range feed is desired, a variety of products can be derived
using a field enhanced separation, such as a separation based on
liquid thermal diffusion. The separation can generate one or more
wax fractions; one or more basestock fractions, including one or
more fractions for various types of basestocks, such as Group I or
Group II/III basestocks; one or more other fractions such as
alkylnaphthalene fractions or diesel fractions; one or more
extender oil fractions; and/or a combination of any of the above.
In some aspects, an advantage of using liquid thermal diffusion for
separation is the ability to separate out fractions that roughly
correspond to various viscosity index (VI) components of a feed. In
the list of fractions mentioned above, the wax fractions represent
the highest VI components, with Group II/III basestocks being next
highest in VI. The trend from high to low VI can continue down
through the various fractions to the extender oil, which represents
the lowest VI fraction.
[0064] One example of a use for a field enhanced separation (such
as a liquid thermal diffusion separation) is to debottleneck
existing solvent extractions units. Using a field enhanced
separation can allow for lower severity conditions and an increase
in yield across existing solvent extraction units. For example, a
liquid thermal diffusion separator can operate on the back end of a
solvent extraction unit to upgrade the resulting viscosity index
(VI) of the raffinate. This can allow the solvent extraction unit
to operate at a lower severity. The liquid thermal diffusion
separator, which is more selective for separating based on VI, can
then perform a final separation to achieve a desired VI value. This
can allow for an increase in yield at a given VI value. In addition
to upgrading the VI of the resulting raffinate, a field enhanced
separation method can also dewax the raffinate at the same time to
produce wax in addition to other products (i.e. Group III lube,
Group II lube, alkylnaphthalenes, Group I lube and extender
oil).
[0065] A field enhanced separation process (such as liquid thermal
diffusion) can also operate on the extract stream from a solvent
dewaxing unit to separate out desirable lubricant boiling range
molecules and/or high VI components from the extract stream.
Without being bound by any particular theory, it is believed that
10%-30% of high VI components are left behind in the extract of a
typical solvent dewaxing process due to the imperfect separation
quality of the solvent extraction process. By separating out high
VI components from the extract, the resulting yield of Group I, II,
or III lube is increased. In addition, the inventive process may
also separate out alkylnaphthalenes and extender oil from the
extract at the same time as separating out the high VI
components.
[0066] More generally, a field enhanced separation process (such as
a liquid thermal diffusion separation process) can be used to
replace a solvent extraction and/or solvent dewaxing process in a
process flow. Both extraction and dewaxing separations can occur
during one stage of a field enhanced separation. In addition,
further processing such as deoiling of wax is typically not
necessary due to the multiple product output streams that can be
generated.
[0067] Another option is to use a liquid thermal diffusion
separator to operate on a slip stream to produce products of
special quality and/or high value which are of limited demand. The
disclosure may also provide blend stocks at a competitive price on
an integrated project economic basis.
[0068] Still another option is to use a liquid thermal diffusion
separator to remove material that could produce deposits, such as
potential contaminant materials encountered in used lubricant
streams and bio-derived streams. In this aspect, the field enhanced
separation would serve as a pretreatment step. A field enhanced
separation may also be used to isolate desired polymers from a
polymer stream.
[0069] A field enhanced separation may also isolate linked ring
structures (C.sub.30-) from a feed. The linked ring structures can
assist in preserving the viscosity of single ring structures.
However, in a conventional separation process, linked ring
structures are often separated from single ring structures based on
boiling point differences or solubility differences. A field
enhanced separator can that generates multiple products can include
one product outflow that is enriched in the desired linked ring
structures.
[0070] A field enhanced separation may include various strategies
to perform a separation and/or concentrate a desired component.
Such strategies may include multi-staging, skimming, reverse
skimming, and recycling. In order to achieve a desired yield of
various products, multi-staging may occur such that more than one
process step is employed. All products, a subset of products, or a
combination of blend components from one unit or stage may enter
into a second unit or stage as incoming feedstock. Multiple stages
may be employed to achieve the desired end result.
[0071] Skimming may occur on a feedstock to selectively remove a
desired component from the bulk feed (i.e. wax). The feedstock may
be any feed containing the desired component (i.e. crude, VGO,
raffinate, bio based feeds, etc.). In contrast, reverse skimming
may include removing the bulk unwanted component(s) from the
feedstock, such as multi-ring aromatics, so as to concentrate high
VI components. Reverse skimming may be combined with multi-staging
such that after the bulk unwanted components are removed in the
first stage, the desired components can be further separated or
refined in subsequent stages. Skimming may also be combined with
multi-staging.
[0072] Recycling is another strategy to concentrate a desired
component. For example, when separating out wax, the first two or
three ports of a thermal diffusion or thermal electric diffusion
separator may contain wax or highly paraffinic components. It may
be desired to separate out all the possible wax molecules in the
bulk feedstock. As a result, one strategy is to collect both as
much wax and as much oil in wax as possible by taking products from
the first several ports as opposed to just the top port which may
be essentially oil free and pure wax. In order to remove the oil in
wax from the ports of interest, it is necessary to recycle a
portion of the stream to further refine the wax and remove the oil.
This method is a strategy to not only separate out more wax
molecules from a feedstock but also a strategy to concentrate the
wax such that it is deoiled with no additional processing steps
required.
[0073] Combinations of strategies may be employed and desired to
achieve necessary yields or specific products. In addition,
strategies may be used to blend components or molecular classes
from the various product ports together in various combinations to
achieve desired yields, product composition of matter, and product
performance. Furthermore, the strategy of blending components from
various ports may be done in combination with multi-staging,
skimming, reverse skimming, and recycling. For example, blends from
one processing step may be used as feed for a second processing
step, a blend may be skimmed or reverse skimmed as well as
recycled.
[0074] In addition to the above strategies, the resulting fractions
or products from thermal diffusion or thermal electric diffusion
can be combined to form various non-contiguous or partially
contiguous fractions. Forming partially contiguous or
non-contiguous fractions can be beneficial for a variety of
reasons. One option is to use a non-contiguous fraction to allow
multiple products to be generated that share a first property, but
that differ in a second property. For example, it may be desirable
to separate a distillate or lubricant base oil boiling range feed
to form multiple fractions that have substantially the same
viscosity index, but that are different in a second property. The
second property can be total product yield; one or more
compositional indicators including but not limited to total
aromatics content, the content of a particular type of aromatic
(such as 1-ring aromatics, 2-ring aromatics, 3-ring aromatics, or
multi-ring aromatics), aliphatic sulfur, total S, total N, or the
ratio of aliphatic sulfur to total sulfur; or one or more
performance indicators, including but not limited to oxidation
stability, deposit tendency, Noack volatility, or a cold flow
property such as pour point or cloud point; or a combination
thereof. In this situation, a first contiguous fraction can be used
that matches the desired first property value. This can represent a
single fraction from the liquid thermal diffusion separator, or a
contiguous/partially contiguous blend from the separator. A second
non-contiguous fraction is then formed that has a value for the
first property that is substantially similar to the value for the
contiguous fraction. Two values are defined to be substantially
similar if the values differ by less than 2.5%, such as by less
than 2.0% or less than 1.5%. For the description herein, the
percentage difference between two values is defined as
(<contiguous property value>-<non-contiguous property
value>)/<contiguous property value>.
[0075] In addition to having similar values for the first property,
the contiguous/partially contiguous fraction and the non-contiguous
fraction have values for a second property that differ by at least
5.0%, such as at least 7.5% or at least 10%. The same definition is
used for determining the percentage difference in values for the
second property.
[0076] Either the first property or the second property can be any
convenient property of interest. Examples of suitable properties
for the first property or the second property include total product
yield and/or compositional/performance indicators, such as
viscosity index, viscosity at 100.degree. C., viscosity at
40.degree. C., pour point, cloud point, Noack volatility, oxidation
stability, deposit tendency, weight percentage of sulfur, ratio of
aliphatic sulfur to total sulfur, weight percentage of nitrogen,
weight percentage of aromatics, or weight percentage of a
particular class of aromatics (such as 1-ring aromatics, 2-ring
aromatics, 3-ring aromatics, or multi-ring aromatics). It is noted
that for properties that correspond to a temperature value, such as
pour point or cloud point, the calculation of the percentage
difference should be performed using an absolute temperature scale.
Thus, pour point or cloud point temperatures should be expressed in
Kelvin rather than degrees Celsius when determining a percentage
difference.
[0077] As another example, non-contiguous and/or partially
contiguous blend fractions can be used to create an enhanced yield
of a product with a given property. Conventionally, the method for
maximizing yield of a product with a given property value is to
separate out the largest contiguous fraction that has the desired
property value. This strategy can be conventionally used with
either a boiling point separation or a liquid thermal diffusion
separation.
[0078] An alternative strategy for increasing yield is to form a
non-contiguous fraction that has the desired property, so that the
non-contiguous fraction can be combined with a contiguous or
partially contiguous fraction that also has the desired property.
In a sense, this corresponds to having a contiguous (or partially
contiguous) fraction and a non-contiguous fraction that have a
substantially similar value for a first property. The second
"property" in this situation is the yield of product with the first
property. The yield of product for the combination of the
contiguous and non-contiguous fraction can be greater than the
maximum yield for a contiguous fraction having the desired property
value.
[0079] It is noted that in this alternative strategy for improving
yield, if the non-contiguous fraction simply represents end
fractions on either side of a middle contiguous fraction, the
requirement of increasing yield will not be satisfied. Instead, the
yields should be identical for the comparison of the middle
contiguous fraction plus end non-contiguous fraction case versus
the single large contiguous fraction case. Thus, an additional
implied constraint on this embodiment is that combining the
non-contiguous fraction with the contiguous fraction should result
in an overall fraction that is either partially contiguous or
preferably non-contiguous.
Configuration Example
Parallel Plates with Spatially Varying Electric Field
[0080] FIG. 6 shows an example of a separator that can use both
liquid thermal diffusion and dielectrophoresis for separation of a
petroleum or hydrocarbon feedstock. In FIG. 6, a separator 600 can
be used for continuous separation of a feedstock into a plurality
of product fractions. Separator 600 includes a hot surface 610 and
a cold surface 620 that are parallel to each other. In the example
shown in FIG. 6, hot surface 610 corresponds to the surface of an
optional protective layer 611, to prevent interaction between hot
surface 610 and the fluid being separated. A similar optional
protective layer could be used to protect cold surface 620. The
bulk material 615 behind hot surface 610 includes a plurality of
heating fluid channels 616 to provide temperature control for hot
surface 610 via heat exchange. The heating fluid channels represent
one possible structure for heating elements to heat a surface in a
field enhanced separation. Other alternatives for heating elements
include resistive heaters located in the bulk material at or behind
surface 610 or any other heating mechanism that allows the
temperature of hot surface 610 to be maintained at a desired level.
The temperature of cold surface 620 can be controlled in a similar
manner. Any convenient fluid can be used as the heat exchange fluid
in channels 616, such as steam or any heat transfer fluid, such as
ethylene glycol and/or silicone heat transfer fluid like
Syltherm.
[0081] The distance between hot surface 610 and cold surface 620
(or between optional protective surfaces 611) defines a gap or
width 650. The fluid for separation is passed in a continuous
manner into gap 650. The separation occurs as the fluid flows
through the channel corresponding to the gap. In FIG. 6, the flow
direction for this channel is perpendicular to the plane of the
page. The width of the gap 650, or alternatively the distance
between hot surface 610 and cold surface 620, can be controlled
using an adjustable spacer or spacers 660.
[0082] In the example shown in FIG. 6, the bulk material 615 behind
hot surface 610 serves as a plate electrode for forming an electric
field across gap 650. Instead of having a plate electrode on the
opposite side, a plurality of point electrodes 670 or other
electrodes corresponding to small protrusions extending past cold
surface 620 are used. These small protrusion or point electrodes
670 can correspond, for example, to protrusions from a circuit
board that resides behind cold surface 620. Using a plurality of
point electrodes 670 opposite a plate electrode (corresponding to
bulk material 615) results in a spatially varying electric field
across gap 650. Either an AC or DC current can be used to charge
the electrodes.
[0083] As an example of how to construct a separator, some
representative distances can be provided for the elements shown in
FIG. 6. The width of gap 650 can be between 0.25 mm and 6.0 mm. The
optional protective layer 611 can be 0.4 mm, so the spacers 660 can
change in width from 0.8 mm to 4.4 mm. The height of the channel
can be 22 inches (559 mm). This would lead to ratios of gap height
to separation volume width of from 2200 (at a width of 0.25 mm) to
193 (at a width of 6.0 mm). Preferably, the separation volume width
can be selected to be at least 1.22 mm, to produce a gap height to
separation volume width ratio of 500 or less. The length
(perpendicular to the plane of the page) for gap 650 can also be 16
inches (406 mm).
[0084] During operation, the fluid flow rate can be selected to
provide a desired residence time for a fluid as it passes through
the channel corresponding to gap 650. A desired residence time
could range from 4 hours to 40 hours, depending on the
corresponding relaxation time required for separation of the fluid
in the channel to reach equilibrium. A plurality of products can be
withdrawn from the exit of the channel (not shown). For example, 7
output ports can be used to withdraw 7 different products from the
channel, with the top output port generating the highest VI product
and the bottom output port generating the lowest VI product.
[0085] As examples of suitable materials for constructing a
separator, the material for forming cold surface 620 (and for
containing electrodes 670) can be a material such as polyethyl
ether ketone (PEEK). Such a material is non-conductive and will not
react with typical petroleum or hydrocarbon feedstocks. The
protective layer 611 can be a glass material or another material
that is non-reactive and non-conductive in the separation
environment. The bulk material 615 can be a material with suitable
heat transfer and electrical properties, such as PEEK. The spacers
can be made of a suitable material, such as Viton.RTM. gasket
material.
Example 1
Separation by Liquid Thermal Diffusion of Dewaxed Vacuum
Distillate
[0086] In this example, a comparison is made between the products
that can be derived from a feed using solvent dewaxing relative to
the products that can be achieved using liquid thermal diffusion
for performing a separation. For comparison purposes, a 130N
dewaxed vacuum distillate was solvent extracted in a conventional
solvent extraction process. Based on the results, the potential
raffinate yield and VI combinations for the process were estimated
for a process including 5-7 theoretical stages. As shown in FIG. 7,
the selected solvent extraction conditions were predicted to result
in a 60% yield of a 91 VI product at 5-7 theoretical solvent
extraction stages. In the limiting case, a maximum possible product
VI was predicted, at a yield of 50%.
[0087] A sample of the 130N dewaxed vacuum distillate was also
separated into fractions by liquid thermal diffusion. A thermal
diffusion column was used to perform the separation. The annular
volume for performing the separation had a separation volume width
of less than 0.33 mm, a height of 72 inches, and a load volume of
30 ml. The temperature differential between the hot and cold
surfaces was 200.degree. F. The separator included 10 output ports
for withdrawing product fractions from the separator.
[0088] After performing the separation for 18 hours, product
fractions were withdrawn from the separator using the output ports.
Based on the number of product fractions that were combined into
the product, several different products could be generated. As
shown in FIG. 7, for the highest VI product, a 46% yield of 125 VI
product was achieved. As noted above, a product with a VI of 125 is
a product that cannot be generated from the 130N dewaxed vacuum
distillate feedstock via solvent extraction/dewaxing. By including
a larger portion of the separation products into the high VI
product, a 64% yield of a 100 VI product or a 69% yield of a 91 VI
product could also be achieved. Based on the results from the
solvent dewaxing, use of a liquid thermal diffusion separation can
provide a 9% yield increase at a constant product VI of 91, or a 4%
yield increase and 9 VI improvement for the 100 VI product.
Example 2
Separation by Liquid Thermal Diffusion of Dewaxed Lubricant Base
Stock Feed
[0089] Column separators for performing liquid thermal diffusion
separations as described above were used to perform separations on
a Group I basestock with a VI of 95 for various lengths of time.
The separation times were 18 hours, 43.5 hours, 89 hours, and 185.5
hours. The temperature differential between the hot and cold
surfaces was 130.degree. F. to 190.degree. F.
[0090] In the following discussion, port 1 of the separator
corresponds to the top output port and port 10 corresponds to the
lowest output port. After the desired separation time for each run,
products were withdrawn from each of the 10 ports. The product
fractions from each port were tested to determine kinematic
viscosity at 40.degree. C. and 100.degree. C., pour point, and
cloud point. During the separations, the output fractions from
ports 1-5 reached equilibrium in 20 hours or less. By contrast,
port 9 did not reach equilibrium until 90 hours. Part of the
difficulty in reaching equilibrium for the product fractions
corresponding to the higher numbered ports may be due to
difficulties in achieving a uniform temperature profile. During the
separations, a uniform temperature profile was not achieved until
18 hours into the separation.
[0091] FIG. 8 shows the viscosity index (VI) for the products
fractions withdrawn from ports 2, 5, and 9 for various run lengths.
The vertical axis shows the VI for the product fraction while the
horizontal axis shows the run length for the corresponding
separation. As shown in FIG. 8, liquid thermal diffusion was
effective for separating the Group I lube feedstock into higher and
lower VI product fractions. The output from port 2 corresponded to
a product fraction with increased VI relative to the feed VI of 95.
The product VI for the port 2 fraction ranged from 130 at 18 hours
to 150 at 180 hours. The output from port 5 also showed an
increased VI relative to the feedstock, with VI values between 100
and 110 depending on the run length. Port 9 showed the largest
changes with increased run length. For the run lengths at 20 and
43.5 hours, the VI of the port 9 product fraction between 60 to 70.
At 90 hours and longer, however, the VI for the product fraction
from port 9 dropped to 10 or less.
[0092] FIG. 9 shows the lubricant basestocks that can be formed by
combining the output fractions from various ports. In FIG. 9, the
yield of a lubricant basestock having a particular VI value is
shown. The farthest right points in the plot represent a product
fraction generated by combining the output of ports 1 and 2 from
the separator. This resulted in a 20% yield of a basestock with
Group III+ equivalent VI. At shorter times, such as 20 hours or
43.5 hours, a 20% yield of a 143 or 145 VI basestock was achieved.
The separation with a run length of 89 hours resulted in a 20%
yield of a basestock with a VI of 155. For the 18 hour run length,
separating out 20% of the feedstock with a 143 VI resulted in a
remaining portion corresponding to 80% of the feedstock that had an
82 VI.
[0093] The middle set of data corresponds to forming a basestock
from the product fractions of ports 1-5. This resulted in a 50%
yield of a basestock with VI equivalent to a Group III basestock.
Again, the VI of this fraction increased with increasing run
length, with a VI of 122 at 20 hours versus a VI of 135 at 89
hours. The leftmost set of data corresponds to forming a basestock
from the product fractions of ports 1-6. This resulted in a 70%
yield of a basestock with VI equivalent to a Group II+ basestock,
with VI values ranging from 110 (20 hours) to 120 (89 hours).
Example 3
Example of Non-Contiguous Blend
[0094] In this example, a lubricant boiling range feed is separated
using a thermal diffusion separation apparatus similar to the
apparatus in Example 2. In this example, it is desired to create
multiple output fractions that have a VI of 117+/-2.5%. In this
example, the fraction from port 2 of the separator corresponds to
the desired VI. A second product with the desired VI is formed by
blending the fraction from port 1, the fraction from port 3, and
85% of the fraction from port 4. Table 1 shows the properties of
the feed, the fraction from port 2, and the non-contiguous blend
fraction.
TABLE-US-00001 TABLE 1 Satu- Ratio of Descrip- rates Aromatics
Total S Aliphatic Total N tion (wt % (wt %) (wt %) S to Total S
(ppm) VI Feed 81.2 17.1 0.430 0.672 27 Port #2 85.8 13.2 0.212
0.759 8.6 117 fraction Blend 85.4 12.9 0.232 0.797 11 119
fraction
[0095] As shown in Table 1, two separate output fractions with a
desired VI are formed. The difference in VI between the two
samples, per the method of calculation defined above, is
(117-119)/117=1.7%. In this example, the ratio of aliphatic sulfur
to total sulfur represents a second property within the output
fractions. The difference in aliphatic sulfur to total sulfur ratio
is (0.759-0.797)/0.759=5.0%. Thus, two separate output fractions
are formed, with a first property (VI) that differs by less than
2.5%, such as less than 2%, while a second property (aliphatic
S/total S) differs by at least 5.0%.
[0096] Tables 2 and 3 show examples of how the ports from a thermal
diffusion unit (TDU) can be used to generate a desired product. In
this example, the desired product is a lubricant basestock output
with a VI of 117. In the TDU, the port heights are adjusted so that
Port 2 generates the desired product. Table 2 shows the output from
ports 1 to 4 of the TDU. In a typical configuration, the thermal
diffusion separation of the feed results in only 3 ml of the
desired product.
TABLE-US-00002 TABLE 2 Feed Charge: Upgraded 30 ml Port 1 Port 2
Port 3 Port 4 Product VI TDU Port 3 ml 3 ml 3 ml 3 ml Output Port
#2 3 ml 3 ml 117 Product
[0097] Table 3 shows an alternative method for using the output
from the same ports for a TDU. In the configuration corresponding
to the outputs in Table 3, the outputs from ports 1, 3, and 4 are
combined to generate additional amounts of the desired product. As
shown in Table 3, in this example a blend using non-contiguous
fractions (ports 1, 3, and 4) produces a product which has the same
desired property VI as the product fraction from port 2. The yield
of this second blend is 6.8 ml. Thus, the total yield of the
desired product with 117 VI is 9.8 ml, as opposed to the 3 ml yield
from only the port 2 product.
TABLE-US-00003 TABLE 3 Feed Charge: Upgraded 30 ml Port 1 Port 2
Port 3 Port 4 Product VI TDU Port 3 ml 3 ml 3 ml 3 ml Output Blend
# 1 2.4 ml 2.4 ml 2 ml 6.8 ml 119 Port # 2 3 ml 3 ml 117 Product
Total Final 11.5 ml Product
Use of Multiple Separation Units for Large Scale Separations
[0098] In order to achieve commercial scale volumes using liquid
thermal separations, a plurality of separation units can be used in
tandem to separate a large input flow. For example, an input
manifold can be used to distribute a large volume of feedstock to a
plurality of separation units that each handle a portion of the
flow. After performing a separation, the resulting product outputs
can be combined using another manifold structure.
Combination of Liquid Thermal Separation and Hydroprocessing
[0099] In some aspects, liquid thermal separation can be used as a
complement to various types of hydroprocessing for producing
desired products, such as lubricant base oils. Conventional
hydroprocessing methods rely on separations based on boiling range
for separating products generated during hydroprocessing. Liquid
thermal separation allows for separation based on alternative
characteristics, such as molecular shape and density. This type of
alternative separation can be integrated with various types of
hydroprocessing reactions.
[0100] In the discussion herein, a stage can correspond to a single
reactor or a plurality of reactors. Optionally, multiple parallel
reactors can be used to perform one or more of the processes, or
multiple parallel reactors can be used for all processes in a
stage. Each stage and/or reactor can include one or more catalyst
beds containing hydroprocessing catalyst. Note that a "bed" of
catalyst in the discussion below can refer to a partial physical
catalyst bed. For example, a catalyst bed within a reactor could be
filled partially with a hydrocracking catalyst and partially with a
dewaxing catalyst. For convenience in description, even though the
two catalysts (such as a hydrocracking catalyst and a dewaxing
catalyst) may be stacked together in a single catalyst bed, the two
catalysts can each be referred to conceptually as separate catalyst
beds.
[0101] Various types of hydroprocessing can be used in the
production of distillate fuels and/or lubricant base oils from a
mineral or biocomponent oil feed. Typical processes include
hydrocracking processes to provide uplift in the viscosity index
(VI) of a feed; dewaxing processes to improve cold flow properties,
such as pour point or cloud point; hydrotreatment processes to
reduce the amount of sulfur, nitrogen, and other impurities in a
feed; and hydrofinishing or aromatic saturation processes for
removing aromatics and olefins from a feed.
Hydrotreatment Conditions
[0102] Hydrotreatment is typically used to reduce the sulfur,
nitrogen, and/or aromatic content of a feed. The catalysts used for
hydrotreatment can include conventional hydrotreatment catalysts,
such as those that comprise at least one Group VIII non-noble metal
(Columns 8-10 of IUPAC periodic table), preferably Fe, Co, and/or
Ni, such as Co and/or Ni; and at least one Group VI metal (Column 6
of IUPAC periodic table), preferably Mo and/or W. Such
hydrotreatment catalysts optionally include transition metal
sulfides that are impregnated or dispersed on a refractory support
or carrier such as alumina and/or silica. The support or carrier
itself typically has no significant/measurable catalytic activity.
Substantially carrier- or support-free catalysts, commonly referred
to as bulk catalysts, generally have higher volumetric activities
than their supported counterparts.
[0103] The catalysts can either be in bulk form or in supported
form. In addition to alumina and/or silica, other suitable
support/carrier materials can include, but are not limited to,
zeolites, titania, silica-titania, and titania-alumina. Suitable
aluminas are porous aluminas such as gamma or eta having average
pore sizes from 50 to 200 .ANG., or 75 to 150 .ANG.; a surface area
from 100 to 300 m.sup.2/g, or 150 to 250 m.sup.2/g; and a pore
volume of from 0.25 to 1.0 cm.sup.3/g, or 0.35 to 0.8 cm.sup.3/g.
More generally, any convenient size, shape, and/or pore size
distribution for a catalyst suitable for hydrotreatment of a
distillate (including lubricant base oil) boiling range feed in a
conventional manner may be used. It is within the scope of the
present disclosure that more than one type of hydroprocessing
catalyst can be used in one or multiple reaction vessels.
[0104] The at least one Group VIII non-noble metal, in oxide form,
can typically be present in an amount ranging from 2 wt % to 30 wt
%, preferably from 4 wt % to 15 wt %. The at least one Group VI
metal, in oxide form, can typically be present in an amount ranging
from 2 wt % to 60 wt %, preferably from 6 wt % to 40 wt % or from
10 wt % to 30 wt %. These weight percents are based on the total
weight of the catalyst. Suitable metal catalysts include
cobalt/molybdenum (1-10% Co as oxide, 10-40% Mo as oxide),
nickel/molybdenum (1-10% Ni as oxide, 10-40% Co as oxide), or
nickel/tungsten (1-10% Ni as oxide, 10-40% W as oxide) on alumina,
silica, silica-alumina, or titania.
[0105] The hydrotreatment is carried out in the presence of
hydrogen. A hydrogen stream is, therefore, fed or injected into a
vessel or reaction zone or hydroprocessing zone in which the
hydroprocessing catalyst is located. Hydrogen, which is contained
in a hydrogen "treat gas," is provided to the reaction zone. Treat
gas, as referred to in this disclosure, can be either pure hydrogen
or a hydrogen-containing gas, which is a gas stream containing
hydrogen in an amount that is sufficient for the intended
reaction(s), optionally including one or more other gasses (e.g.,
nitrogen and light hydrocarbons such as methane), and which will
not adversely interfere with or affect either the reactions or the
products. Impurities, such as H.sub.2S and NH.sub.3 are undesirable
and would typically be removed from the treat gas before it is
conducted to the reactor. The treat gas stream introduced into a
reaction stage will preferably contain at least 50 vol. % and more
preferably at least 75 vol. % hydrogen.
[0106] Hydrogen can be supplied at a rate of from 100 SCF/B
(standard cubic feet of hydrogen per barrel of feed) (17.8
Nm.sup.3/m.sup.3) to 10000 SCF/B (1781 Nm.sup.3/m.sup.3).
Preferably, the hydrogen is provided in a range of from 200 SCF/B
(34 Nm.sup.3/m.sup.3) to 1500 SCF/B (253 Nm.sup.3/m.sup.3).
Hydrogen can be supplied co-currently with the input feed to the
hydrotreatment reactor and/or reaction zone or separately via a
separate gas conduit to the hydrotreatment zone.
[0107] Hydrotreating conditions can include temperatures of
200.degree. C. to 450.degree. C., or 315.degree. C. to 425.degree.
C.; pressures of 250 psig (1.8 MPag) to 5000 psig (34.6 MPag) or
300 psig (2.1 MPag) to 3000 psig (20.8 MPag); liquid hourly space
velocities (LHSV) of 0.1 hr.sup.-1 to 10 hr.sup.-1; and hydrogen
treat rates of 100 scf/B (17.8 m.sup.3/m.sup.3) to 10,000 scf/B
(1781 m.sup.3/m.sup.3), or 500 (89 m.sup.3/m.sup.3) to 10,000 scf/B
(1781 m.sup.3/m.sup.3).
Hydrocracking Conditions
[0108] Hydrocracking of a feed is typically performed when
conversion of higher boiling molecules in a feedstock to lower
boiling molecules is desired. During such a conversion process,
other properties of a feedstock may also be affected, such the
viscosity index of a feed. Conversion of the feed can be defined in
terms of conversion of molecules that boil above a temperature
threshold to molecules below that threshold. The conversion
temperature can be any convenient temperature, such as 700.degree.
F. (371.degree. C.).
[0109] Hydrocracking catalysts typically contain sulfided base
metals on acidic supports, such as amorphous silica alumina,
cracking zeolites such as USY, or acidified alumina. Often these
acidic supports are mixed or bound with other metal oxides such as
alumina, titania or silica. Non-limiting examples of metals for
hydrocracking catalysts include nickel, nickel-cobalt-molybdenum,
cobalt-molybdenum, nickel-tungsten, nickel-molybdenum, and/or
nickel-molybdenum-tungsten. Additionally or alternately,
hydrocracking catalysts with noble metals can also be used.
Non-limiting examples of noble metal catalysts include those based
on platinum and/or palladium. Support materials which may be used
for both the noble and non-noble metal catalysts can comprise a
refractory oxide material such as alumina, silica, alumina-silica,
kieselguhr, diatomaceous earth, magnesia, zirconia, or combinations
thereof, with alumina, silica, alumina-silica being the most common
(and preferred, in one embodiment). It is noted that some
conventional hydrotreating catalysts are also suitable for
performing hydrocracking under sufficiently severe conditions.
[0110] In various embodiments, the conditions selected for
hydrocracking for lubricant base oil production can depend on the
desired level of conversion, the level of contaminants in the input
feed to the hydrocracking stage, and potentially other factors.
[0111] A hydrocracking process performed under sour conditions,
such as conditions where the sulfur content of the input feed to
the hydrocracking stage is at least 500 wppm, can be carried out at
temperatures of 550.degree. F. (288.degree. C.) to 840.degree. F.
(449.degree. C.), hydrogen partial pressures of from 250 psig to
5000 psig (1.8 MPag to 34.6 MPag), liquid hourly space velocities
of from 0.05 h.sup.-1 to 10 h.sup.-1, and hydrogen treat gas rates
of from 35.6 m.sup.3/m.sup.3 to 1781 m.sup.3/m.sup.3 (200 SCF/B to
10,000 SCF/B). In other embodiments, the conditions can include
temperatures in the range of 600.degree. F. (343.degree. C.) to
815.degree. F. (435.degree. C.), hydrogen partial pressures of from
500 psig to 3000 psig (3.5 MPag-20.9 MPag), liquid hourly space
velocities of from 0.2 h.sup.-1 to 2 h.sup.-1 and hydrogen treat
gas rates of from 213 m.sup.3/m.sup.3 to 1068 m.sup.3/m.sup.3 (1200
SCF/B to 6000 SCF/B).
[0112] A hydrocracking process performed under non-sour conditions
can be performed under conditions similar to those used for a first
stage hydrocracking process, or the conditions can be different.
Alternatively, a non-sour hydrocracking stage can have less severe
conditions than a similar hydrocracking stage operating under sour
conditions. Suitable hydrocracking conditions can include
temperatures of 550.degree. F. (288.degree. C.) to 840.degree. F.
(449.degree. C.), hydrogen partial pressures of from 250 psig to
5000 psig (1.8 MPag to 34.6 MPag), liquid hourly space velocities
of from 0.05 h.sup.-1 to 10 h.sup.-1, and hydrogen treat gas rates
of from 35.6 m.sup.3/m.sup.3 to 1781 m.sup.3/m.sup.3 (200 SCF/B to
10,000 SCF/B). In other embodiments, the conditions can include
temperatures in the range of 600.degree. F. (343.degree. C.) to
815.degree. F. (435.degree. C.), hydrogen partial pressures of from
500 psig to 3000 psig (3.5 MPag-20.9 MPag), liquid hourly space
velocities of from 0.2 h.sup.-1 to 2 h.sup.-1 and hydrogen treat
gas rates of from 213 m.sup.3/m.sup.3 to 1068 m.sup.3/m.sup.3 (1200
SCF/B to 6000 SCF/B). In some embodiments, multiple hydrocracking
stages may be present, with a first hydrocracking stage operating
under sour conditions, while a second hydrocracking stage operates
under non-sour conditions and/or under conditions where the sulfur
level is substantially reduced relative to the first hydrocracking
stage. In such embodiments, the temperature in the second stage
hydrocracking process can be 40.degree. F. (22.degree. C.) less
than the temperature for a hydrocracking process in the first
stage, or 80.degree. F. (44.degree. C.) less, or 120.degree. F.
(66.degree. C.) less. The pressure for the second stage
hydrocracking process can be 100 psig (690 kPa) less than a
hydrocracking process in the first stage, or 200 psig (1380 kPa)
less, or 300 psig (2070 kPa) less.
[0113] In still another embodiment, the same conditions can be used
for hydrotreating and hydrocracking beds or stages, such as using
hydrotreating conditions for both or using hydrocracking conditions
for both. In yet another embodiment, the pressure for the
hydrotreating and hydrocracking beds or stages can be the same.
Catalytic Dewaxing Process
[0114] In order to enhance diesel production and to improve the
quality of lubricant base oils produced from a reaction system, at
least a portion of the catalyst in the reaction system can be a
dewaxing catalyst. Suitable dewaxing catalysts can include
molecular sieves such as crystalline aluminosilicates (zeolites).
In an embodiment, the molecular sieve can comprise, consist
essentially of, or be ZSM-5, ZSM-22, ZSM-23, ZSM-35, ZSM-48,
zeolite Beta, or a combination thereof, for example ZSM-23 and/or
ZSM-48, or ZSM-48 and/or zeolite Beta. Optionally but preferably,
molecular sieves that are selective for dewaxing by isomerization
as opposed to cracking can be used, such as ZSM-48, zeolite Beta,
ZSM-23, or a combination thereof. Additionally or alternately, the
molecular sieve can comprise, consist essentially of, or be a
10-member ring 1-D molecular sieve. Examples include EU-1, ZSM-35
(or ferrierite), ZSM-11, ZSM-57, NU-87, SAPO-11, ZSM-48, ZSM-23,
and ZSM-22. Preferred materials are EU-2, EU-11, ZBM-30, ZSM-48, or
ZSM-23. ZSM-48 is most preferred. Note that a zeolite having the
ZSM-23 structure with a silica to alumina ratio of from 20:1 to
40:1 can sometimes be referred to as SSZ-32. Other molecular sieves
that are isostructural with the above materials include Theta-1,
NU-10, EU-13, KZ-1, and NU-23. Optionally but preferably, the
dewaxing catalyst can include a binder for the molecular sieve,
such as alumina, titania, silica, silica-alumina, zirconia, or a
combination thereof, for example alumina and/or titania or silica
and/or zirconia and/or titania.
[0115] Preferably, the dewaxing catalysts used in processes
according to the disclosure are catalysts with a low ratio of
silica to alumina. For example, for ZSM-48, the ratio of silica to
alumina in the zeolite can be less than 200:1, or less than 110:1,
or less than 100:1, or less than 90:1, or less than 80:1. In
various embodiments, the ratio of silica to alumina can be from
30:1 to 200:1, 60:1 to 110:1, or 70:1 to 100:1.
[0116] In various embodiments, the catalysts according to the
disclosure further include a metal hydrogenation component. The
metal hydrogenation component is typically a Group VI and/or a
Group VIII metal. Preferably, the metal hydrogenation component is
a Group VIII noble metal. Preferably, the metal hydrogenation
component is Pt, Pd, or a mixture thereof. In an alternative
preferred embodiment, the metal hydrogenation component can be a
combination of a non-noble Group VIII metal with a Group VI metal.
Suitable combinations can include Ni, Co, or Fe with Mo or W,
preferably Ni with Mo or W.
[0117] The metal hydrogenation component may be added to the
catalyst in any convenient manner. One technique for adding the
metal hydrogenation component is by incipient wetness. For example,
after combining a zeolite and a binder, the combined zeolite and
binder can be extruded into catalyst particles. These catalyst
particles can then be exposed to a solution containing a suitable
metal precursor. Alternatively, metal can be added to the catalyst
by ion exchange, where a metal precursor is added to a mixture of
zeolite (or zeolite and binder) prior to extrusion.
[0118] The amount of metal in the catalyst can be at least 0.1 wt %
based on catalyst, or at least 0.15 wt %, or at least 0.2 wt %, or
at least 0.25 wt %, or at least 0.3 wt %, or at least 0.5 wt %
based on catalyst. The amount of metal in the catalyst can be 20 wt
% or less based on catalyst, or 10 wt % or less, or 5 wt % or less,
or 2.5 wt % or less, or 1 wt % or less. For embodiments where the
metal is Pt, Pd, another Group VIII noble metal, or a combination
thereof, the amount of metal can be from 0.1 to 5 wt %, preferably
from 0.1 to 2 wt %, or 0.25 to 1.8 wt %, or 0.4 to 1.5 wt %. For
embodiments where the metal is a combination of a non-noble Group
VIII metal with a Group VI metal, the combined amount of metal can
be from 0.5 wt % to 20 wt %, or 1 wt % to 15 wt %, or 2.5 wt % to
10 wt %.
[0119] The dewaxing catalysts useful in processes according to the
disclosure can also include a binder. In some embodiments, the
dewaxing catalysts used in process according to the disclosure are
formulated using a low surface area binder, a low surface area
binder represents a binder with a surface area of 100 m.sup.2/g or
less, or 80 m.sup.2/g or less, or 70 m.sup.2/g or less.
[0120] A zeolite can be combined with binder in any convenient
manner. For example, a bound catalyst can be produced by starting
with powders of both the zeolite and binder, combining and mulling
the powders with added water to form a mixture, and then extruding
the mixture to produce a bound catalyst of a desired size.
Extrusion aids can also be used to modify the extrusion flow
properties of the zeolite and binder mixture. The amount of
framework alumina in the catalyst may range from 0.1 to 3.33 wt %,
or 0.1 to 2.7 wt %, or 0.2 to 2 wt %, or 0.3 to 1 wt %.
[0121] Process conditions in a catalytic dewaxing zone in a sour
environment can include a temperature of from 200 to 450.degree.
C., preferably 270 to 400.degree. C., a hydrogen partial pressure
of from 1.8 MPag to 34.6 MPag (250 psig to 5000 psig), preferably
4.8 MPag to 20.8 MPag, a liquid hourly space velocity of from 0.2
hr.sup.-1 to 10 hr.sup.-1, preferably 0.5 hr.sup.-1 to 3.0
hr.sup.-1, and a hydrogen circulation rate of from 35.6
m.sup.3/m.sup.3 (200 SCF/B) to 1781 m.sup.3/m.sup.3 (10,000 scf/B),
preferably 178 m.sup.3/m.sup.3 (1000 SCF/B) to 890.6
m.sup.3/m.sup.3 (5000 SCF/B). In still other embodiments, the
conditions can include temperatures in the range of 600.degree. F.
(343.degree. C.) to 815.degree. F. (435.degree. C.), hydrogen
partial pressures of from 500 psig to 3000 psig (3.5 MPag-20.9
MPag), and hydrogen treat gas rates of from 213 m.sup.3/m.sup.3 to
1068 m.sup.3/m.sup.3 (1200 SCF/B to 6000 SCF/B). These latter
conditions may be suitable, for example, if the dewaxing stage is
operating under sour conditions.
[0122] Additionally or alternately, the conditions for dewaxing can
be selected based on the conditions for a preceeding reaction in
the stage, such as hydrocracking conditions or hydrotreating
conditions. Such conditions can be further modified using a quench
between previous catalyst bed(s) and the bed for the dewaxing
catalyst. Instead of operating the dewaxing process at a
temperature corresponding to the exit temperature of the prior
catalyst bed, a quench can be used to reduce the temperature for
the hydrocarbon stream at the beginning of the dewaxing catalyst
bed. One option can be to use a quench to have a temperature at the
beginning of the dewaxing catalyst bed that is the same as the
inlet temperature of the prior catalyst bed. Another option can be
to use a quench to have a temperature at the beginning of the
dewaxing catalyst bed that is at least 10.degree. F. (6.degree. C.)
lower than the prior catalyst bed, or at least 20.degree. F.
(11.degree. C.) lower, or at least 30.degree. F. (16.degree. C.)
lower, or at least 40.degree. F. (21.degree. C.) lower.
[0123] As still another option, the dewaxing catalyst in the final
reaction stage can be mixed with another type of catalyst, such as
hydrocracking catalyst, in at least one bed in a reactor. As yet
another option, a hydrocracking catalyst and a dewaxing catalyst
can be co-extruded with a single binder to form a mixed
functionality catalyst.
Hydrofinishing and/or Aromatic Saturation Process
[0124] In some aspects, a hydrofinishing and/or aromatic saturation
stage can also be provided. Typically, a hydrofinishing and/or
aromatic saturation can occur after the last hydrocracking or
dewaxing stage, but other locations for a hydrofinishing stage in a
reaction system may also be suitable. The hydrofinishing and/or
aromatic saturation can occur either before or after fractionation.
If hydrofinishing and/or aromatic saturation occurs after
fractionation, the hydrofinishing can be performed on one or more
portions of the fractionated product, such as being performed on
the bottoms from the reaction stage (i.e., the hydrocracker
bottoms). Alternatively, the entire effluent from the last
hydrocracking or dewaxing process can be hydrofinished and/or
undergo aromatic saturation.
[0125] In some situations, a hydrofinishing process and an aromatic
saturation process can refer to a single process performed using
the same catalyst. Alternatively, one type of catalyst or catalyst
system can be provided to perform aromatic saturation, while a
second catalyst or catalyst system can be used for hydrofinishing.
Typically a hydrofinishing and/or aromatic saturation process will
be performed in a separate reactor from dewaxing or hydrocracking
processes for practical reasons, such as facilitating use of a
lower temperature for the hydrofinishing or aromatic saturation
process. However, an additional hydrofinishing reactor following a
hydrocracking or dewaxing process but prior to fractionation could
still be considered part of a second stage of a reaction system
conceptually.
[0126] Hydrofinishing and/or aromatic saturation catalysts can
include catalysts containing Group VI metals, Group VIII metals,
and mixtures thereof. In an embodiment, preferred metals include at
least one metal sulfide having a strong hydrogenation function. In
another embodiment, the hydrofinishing catalyst can include a Group
VIII noble metal, such as Pt, Pd, or a combination thereof. The
mixture of metals may also be present as bulk metal catalysts
wherein the amount of metal is 30 wt. % or greater based on
catalyst. Suitable metal oxide supports include low acidic oxides
such as silica, alumina, silica-aluminas or titania, preferably
alumina. The preferred hydrofinishing catalysts for aromatic
saturation will comprise at least one metal having relatively
strong hydrogenation function on a porous support. Typical support
materials include amorphous or crystalline oxide materials such as
alumina, silica, and silica-alumina. The support materials may also
be modified, such as by halogenation, or in particular
fluorination. The metal content of the catalyst is often as high as
20 weight percent for non-noble metals. In an embodiment, a
preferred hydrofinishing catalyst can include a crystalline
material belonging to the M41S class or family of catalysts. The
M41S family of catalysts are mesoporous materials having high
silica content. Examples include MCM-41, MCM-48 and MCM-50. A
preferred member of this class is MCM-41. If separate catalysts are
used for aromatic saturation and hydrofinishing, an aromatic
saturation catalyst can be selected based on activity and/or
selectivity for aromatic saturation, while a hydrofinishing
catalyst can be selected based on activity for improving product
specifications, such as product color and polynuclear aromatic
reduction.
[0127] Hydrofinishing conditions can include temperatures from
125.degree. C. to 425.degree. C., preferably 180.degree. C. to
280.degree. C., a hydrogen partial pressure from 500 psig (3.4 MPa)
to 3000 psig (20.7 MPa), preferably 1500 psig (10.3 MPa) to 2500
psig (17.2 MPa), and liquid hourly space velocity from 0.1
hr.sup.-1 to 5 hr.sup.-1 LHSV, preferably 0.5 hr.sup.-1 to 1.5
hr.sup.-1. Additionally, a hydrogen treat gas rate of from 35.6
m.sup.3/m.sup.3 to 1781 m.sup.3/m.sup.3 (200 SCF/B to 10,000 SCF/B)
can be used.
Configuration Example 4
Efficient Product Separation Using Liquid Thermal Diffusion
[0128] FIGS. 10-14 schematically show various process
configurations suitable for combining hydroprocessing of a
feedstock with liquid thermal diffusion. Of course, the
configurations shown in FIGS. 10-14 are exemplary, and use of
liquid thermal diffusion with hydroprocessing is not limited to
only the configurations shown in FIGS. 10-14.
[0129] FIG. 10 provides a basic configuration for performing
hydroprocessing in conjunction with use of a liquid thermal
diffusion separator. In FIG. 10, a hydroprocessing reactor 1010 is
used to hydroprocess a feedstock 1005. An example of a suitable
feedstock is a vacuum gas oil, a vacuum bottoms and/or asphalt
feed, a light neutral distillate, a light cycle oil, a slack wax
and/or Fischer-Tropsch wax stream, a biologically-derived oil
and/or wax, or a combination thereof. Additionally or alternately,
the feedstock can be defined based on a boiling range, as
previously described.
[0130] The effluent 1015 from hydroprocessing reactor 1010 is then
passed into one or more liquid thermal diffusion separators 1070.
Optionally, the effluent 1015 can be separated 1018 prior to
entering liquid thermal diffusion separator 1070 to remove lower
boiling components, such as light ends and/or naphtha boiling range
components. A gas-liquid separator, a flash separator, a high
pressure separator, or other types of separation devices may be
suitable for performing the separation. The liquid thermal
diffusion separator 1070 generates a plurality of output streams or
products. In the example shown in FIG. 10, 6 output streams are
shown. These products correspond to a wax output 1071, an output
1073 with properties suitable for use as a feed for making Group
II/Group III lubricant base oils, an alkylnaphthalene output 1075,
a diesel or distillate fuel output 1076, an extender oil product
1078, and an output 1079 containing the lowest viscosity index (VI)
portions of the effluent 1015. This low VI output 1079 may
sometimes be referred to as an "extract" output. In various other
aspects, different numbers and/or types of outputs can be generated
as desired. Thus, the 6 output streams 1071, 1073, 1075, 1076,
1078, and 1079 are representative of the variety of potential
output streams that can be produced.
[0131] The output streams from liquid thermal diffusion
separator(s) 1070 can be used for a variety of purposes. Wax stream
1071 and lubricant base oil stream 1073 represent high viscosity
index streams that are separated out using liquid thermal diffusion
separator 1070. Alkylnaphthalenes 1075 may be useful for blending
either with a lubricant base oil product or with a diesel product.
Distillate fuel product 1076 can include both diesel and kerosene
fractions, depending on the input feed provided to the separation.
Extender oil 1078 and extract 1079 can be used as fuel oils or for
other lower value purposes.
[0132] In one aspect, hydroprocessing can be used in combination
with liquid thermal diffusion based on a single pass of a feedstock
1005 through the hydroprocessing reaction 1010 and the liquid
thermal diffusion separator(s) 1070. For example, a vacuum gas oil
feed, optionally blended with other distillate boiling range
components, can be used as the feed 1005. The hydroprocessing
reactor 1010 can be used to hydrotreat the feed under effective
hydrotreating conditions. This results in a modest amount of
conversion of the feed relative to a 700.degree. F. (371.degree.
C.) boiling point, as well as removal of contaminants such as
sulfur and nitrogen. Some aromatic saturation may also occur. In
this aspect, effluent 1015 corresponds to a hydrotreated effluent.
The liquid thermal diffusion separator(s) 1070 can then separate
the hydrotreated effluent 1015, after optional separation 1018 to
remove low boiling components. The liquid thermal diffusion
separation results in a plurality of products or outputs, such as
the outputs 1071, 1073, 1075, 1076, 1078, and 1079 shown in FIG.
10.
[0133] In some optional aspects, a portion of the output from the
liquid thermal separator 1070 can be recycled for combination with
feed 1005. In these types of optional aspects, higher VI components
would not be recycled, as these are high value products. Thus,
components with a VI of at least 80, preferably at least 90, such
as at least 100, are not recycled. Additionally, components with a
low VI, such as components with a VI of 40 or less, such as 30 or
less, are also not recycled. The remaining intermediate VI products
can be recycled for further hydroprocessing, in order to upgrade
the intermediate VI products to products with higher viscosity
index. In FIG. 10, portions of the outputs from liquid thermal
diffusion separator 1070 are shown as potential candidates for
recycle. In the example shown in FIG. 10, output portion 1082
corresponds to a portion of the alkylnaphthalene output 1075 and
diesel output 1076, although a portion of lubricant base oil output
1073 may also be included. When recycle is desired, a recycle
stream 1084 is formed from output portion 1082 and combined with
feedstock 1005 into hydroprocessing reaction 1010. One way of
determining if recycle is desired is to perform recycle so long as
the recycle increases the amount of high VI product in the output
of the liquid thermal separator 1070. When addition of recycle
stream 1084 to feedstock 1005 does not result in an increase in
high VI product, the output portion 1082 can instead by used as an
output or product stream 1087.
[0134] In aspects where an output portion 1082 is recycled,
hydroprocessing reactor 1010 can correspond to a variety of types
of hydroprocessing, such as hydroconversion (either hydrotreatment
or hydrocracking) or catalytic dewaxing (or other types of
hydroisomerization). In an alternative embodiment, the
configuration in FIG. 10 can also be used with an asphalt
feedstock, with reactor 1010 corresponding to an air blower rather
than a hydroprocessing unit.
Configuration Example 5
Enriching Feedstock with Desired Components for Hydroprocessing
[0135] FIG. 11 schematically shows another configuration for using
hydroprocessing in conjunction with separation by liquid thermal
diffusion. In the types of configurations represented by FIG. 11, a
feedstock is separated using liquid thermal diffusion so that
hydroprocessing is performed on only a portion of the feedstock. In
some aspects, a feedstock can be split into two portions for
processing. A first portion can be separated using liquid thermal
diffusion while a second portion is directly passed into one or
more hydroprocessing stages. After separation, one or more outputs
from the liquid thermal diffusion separator can be used to enhance
the content of certain types of molecules in the second portion.
For example, a liquid thermal diffusion separation can be used on a
portion of a feedstock to isolate high viscosity index components,
such as waxy components or lubricant base oil components. These
isolated high VI components can then be added to a remaining
portion of the feedstock to provide a feedstock for hydroprocessing
that is enriched in components suitable for making lubricant base
oils.
[0136] In FIG. 11, a feedstock 1105 can initially undergo an
optional hydrotreatment 1120. The feedstock 1105 can be a vacuum
gas oil or another type of distillate and/or gas oil boiling range
feedstock. Optionally, the feedstock 1105 can also include some
molecules that would correspond to vacuum bottoms boiling range
material. In aspects where hydrotreatment 1120 is not used,
feedstock 1105 can be passed directly into liquid thermal diffusion
separator 1070. As shown in FIG. 11, feedstock 1105 is initially
hydrotreated 1120, and the hydrotreated effluent is passed into
liquid thermal diffusion separator 1070. Optionally, the
hydrotreated effluent can undergo a flash or gas-liquid separation
to remove lower boiling components before being passed into liquid
thermal diffusion separator 1070. The liquid thermal diffusion
separator 1070 generates a plurality of output streams, such as
outputs 1071, 1073, 1075, 1076, 1078, and 1079.
[0137] Portions of the one or more of the products from liquid
thermal diffusion separator 1070 can then undergo further
hydroprocessing. One option is to perform additional hydrotreatment
1140 on a diesel or distillate fuel product 1076. This results in a
hydrotreated diesel or distillate fuel product 1142. Another option
is to perform additional hydroprocessing on at least a portion of
wax output 1071 and/or lubricant base oil output 1073. If only a
portion of wax output 1071 is exposed to further hydroprocessing,
the remaining portion 1191 may be used directly as a product or as
an input for other processes. Similarly, if only a portion of
lubricant base oil output 1073 is exposed to further
hydroprocessing, the remaining portion 1193 may be used directly as
a product or as an input for other processes.
[0138] The portions of outputs 1071 and 1073 that are exposed to
further hydroprocessing correspond to stream 1182, which is then
hydroprocessed in reactor or reaction stages 1130. Typically,
stream 1182 will represent less than half by weight of the input
flow to hydroprocessing reactor 1130. For example, if feedstock
1105 is hydrotreated 1120, then portion 1124 that is passed into
liquid thermal separator 1070 will typically represent less than
half of the weight of hydrotreated effluent 1122. The remaining
portion of effluent 1122 forms an input stream 1128 for
hydroprocessing 1130. Additionally or alternately, additional
feedstock 1135 can be introduced into hydroprocessing reactor 1130.
If feedstock 1105 is not hydrotreated prior to entering separator
1070, then the weight of feedstock 1105 will typically be less than
the weight of feedstock 1135. In some aspects, feedstock 1105 and
feedstock 1135 can be derived from a common source of feedstock,
such as corresponding to the same vacuum gas oil or other
distillate/gas oil boiling range feed.
[0139] Input stream 1182, along with at least one of hydrotreated
effluent portion 1128 or feedstock 1135, are then hydroprocessed
1130. A variety of types of hydroprocessing may be performed in the
reaction stages corresponding to hydroprocessing reactor 1130.
Suitable types of hydroprocessing include hydrotreatment to reduce
contaminant levels, hydrocracking for VI uplift, and dewaxing to
improve cold flow properties. For example, in some aspects an
initial hydrotreatment 1120 may not be performed, so that the
inputs to hydroprocessing 1130 are stream 1182 and feedstock 1135.
In such aspects, hydroprocessing reactor 1130 can include one or
more initial stages for hydrotreatment followed by one or more
stages of hydrocracking and/or catalytic dewaxing. If an initial
hydrotreatment 1120 is performed (or if feedstocks 1105 and 1135
have sufficiently low contents of contaminant species), additional
hydrotreatment in hydroprocessing reaction stages 1130 may not be
necessary, so that hydroprocessing 1130 corresponds to one or more
stages of hydrocracking, one or more stages of catalytic dewaxing,
or a combination thereof. The outputs from hydroprocessing 1130 can
correspond to diesel or distillate fuel output 1132 and lubricant
base oil output 1134. In many aspects, diesel output 1132 may
correspond to a diesel with improved pour point or other low
temperature properties, due to at least one catalytic dewaxing
stage being present in hydroprocessing reaction stages 1130.
Similarly, lubricant base oil output 1134 may be suitable for use
as a Group II+ or Group III base oil. In various aspects, one or
more hydrofinishing stages may also be included as part of
hydroprocessing 1130. Alternatively, hydrofinishing may be
performed on one of the output streams from hydroprocessing 1130,
such as lubricant base oil output 1134.
Configuration Example 6
Process Stage Bypass Configurations
[0140] FIG. 12 shows an example of a configuration where portions
of a feed are allowed to bypass one or more hydroprocessing stages.
Bypass of processing stages can be used to allow for processing of
two different types of feedstocks, with one feedstock being passed
into a reaction system at a downstream stage of hydroprocessing.
One way of generating two different types of feedstocks is to start
with a single feedstock and perform a liquid thermal diffusion
separation on a portion of the feed. This can allow for separation
out or selection of desired portions of the feed, such as a portion
suitable for forming lubricant base oils. This selected portion of
the feed can then be treated using additional hydroprocessing
stages, while the main portion of the feedstock is exposed to a
more limited form of hydroprocessing. These types of configurations
can allow hydroprocessing reactions to be targeted to higher value
portions of a feedstock, thus reducing or avoiding excess
processing of lower value portions of a feed.
[0141] In FIG. 12, an initial hydrotreatment can be performed 1220
on a feedstock 1205. The feedstock 1205 can be any suitable
feedstock, such as a vacuum gas oil feed or a vacuum gas oil feed
blended with one or more other feeds. At least a portion of the
resulting hydrotreated effluent 1222 can then be used as an input
stream 1228 for further hydroprocessing. Depending on the aspect,
all of input stream 1228 can be exposed to all of the beds in
hydroprocessing reaction stages 1250. Alternatively, a portion of
input stream 1228 can be diverted to form a bypass stream 1255 that
bypasses one or more catalyst beds or reaction stages. Optionally,
an additional feedstock stream 1256 can also be introduced into
reaction stages 1250, either for exposure to all reaction stages or
as a bypass stream.
[0142] The effluent from reaction stages 1250 can be handled in
various ways. As shown in FIG. 12, a portion of the effluent from
reaction stages 1250 can be used as an input stream 1254 for a
conventional fractionator, in order to form distillate fuel and/or
lubricant base oil fractions. The remaining portion of the effluent
from reaction stages 1250 can be used as an input stream 1252 for a
liquid thermal diffusion separator 1070.
[0143] The hydroprocessing in hydroprocessing stages 1250 can be of
any convenient type. Suitable reaction stages include
hydrotreatment, hydrocracking, and catalytic dewaxing stages. For
example, the hydroprocessing stages 1250 can correspond to one or
more first catalytic dewaxing stages, one or more hydrocracking
stages, and one or more second catalytic dewaxing stages. The
bypass stream 1255 can bypass at least a portion of the first
catalytic dewaxing stages, or the bypass stream 1255 can bypass
both the first catalytic dewaxing stages and at least a portion of
the hydrocracking stages. Alternatively, reaction stages 1250 can
correspond to one or more hydrocracking stages or a combination of
hydrotreating and hydrocracking stages. Still another option is to
use any desired combination of hydrotreating, hydrocracking, and
catalytic dewaxing stages.
[0144] In some aspects, a portion of hydrotreated effluent 1222 can
be used to form a side stream 1224. The side stream 1224 can be
passed into another liquid thermal diffusion separator 1270 in
order to form a stream 1282 that can increase the quantity of a
desired component in stream 1228, stream 1255, or another input
stream to reaction stages 1250. As shown in FIG. 12, stream
corresponds to a wax stream while stream 1273 corresponds to a
stream suitable for forming lubricant base oils. Portions of these
streams can be used as output or product streams 1291 and 1293. The
remainder of these streams can be used to form stream 1282 for
enriching the input to hydroprocessing stages 1250. Other possible
representative outputs from separation 1270 of the side stream 1224
are alkylnaphthalenes 1275, distillate fuels 1276, extender oil
1278, and extract 1279.
Configuration Example 7
Combination of Temperature Fractionation and Liquid Thermal
Diffusion Separation
[0145] Still another option is to use both separations based on
boiling range and separations based on liquid thermal diffusion to
achieve a desired product slate. FIGS. 13 and 14 show examples of
configurations where an atmospheric distillation unit is used in
combination with a liquid thermal diffusion separator to generate
various outputs. These types of aspects reduce the total volume of
the outputs that are processed using liquid thermal diffusion while
still allowing for production of outputs not conventionally
available using only a temperature based fractionation.
[0146] In FIG. 13, a feedstock 1305 is hydrotreated 1320 to remove
contaminants. Optionally, a portion of hydrotreatment stage 1320
can also include another type of hydroprocessing catalyst, such as
hydrocracking catalyst. The hydrotreated effluent 1322 can then be
hydroprocessed 1350, such as by catalytic dewaxing, hydrocracking,
and/or hydrofinishing. For example, the hydrotreated effluent can
be catalytically dewaxed in a first stage, hydrocracked in a second
stage, and catalytically dewaxed in a third stage. Optionally, a
portion of hydrotreated effluent 1322 can be used to form a bypass
input 1355 that bypasses one or more stages of hydroprocessing
stages 1350.
[0147] The effluent 1352 from hydroprocessing stages 1350 can then
be fractionated 1360, such as by using an atmospheric distillation
unit. An initial gas-liquid separator can optionally be used to
remove light ends and/or naphtha boiling range molecules before
effluent 1352 enters fractionator 1360. The fractionator 1360 can
separate the effluent 1352 into one or more fuels output streams
1352, such as one or more kerosene outputs and one or more diesel
outputs. A bottoms portion 1364 from fractionator 1360 can then be
used as the input for a liquid thermal diffusion separator 1370.
The bottoms portion can correspond, for example, to a 700.degree.
F.+ (371.degree. C.+) portion of the effluent 1352. The liquid
thermal diffusion separator 1370 can separate the bottoms portion
1364 into any convenient number of output streams. For example,
FIG. 13 shows formation of a lubricant base oil output 1373 and an
alkylnaphthalene output 1375. The liquid thermal diffusion
separator 1370 may also produce one or more additional outputs
corresponding to lower value molecules in the bottoms portion 1364.
It is noted that the diesel portion of the hydroprocessing effluent
1352 was already removed by fractionator 1360.
[0148] FIG. 14 shows an alternative configuration where similar
processing stages are used, but the stages are organized
differently. In FIG. 14, a feedstock 1405 is hydrotreated 1420. The
hydrotreated effluent 1422 is combined with a hydroprocessed output
1458. The combined stream, after optional separation to remove low
boiling molecules, is passed into a fractionator 1460, such as an
atmospheric distillation unit. This results in one or more output
streams, such as a distillate fuel output 1462. The bottoms portion
1464 is then split to form an input stream for hydroprocessing unit
1450 and a stream 1468 for separation in a liquid thermal diffusion
separator 1070. The extract portion 1479 from separator 1070 is
recycled and added to the input stream to hydroprocessing stages
1450. Optionally, a portion of the input stream to hydroprocessing
stages 1450 can be used to form a bypass stream 1455 that bypasses
one or more of the hydroprocessing stages. By using the extract
1479 from separator 1070 as a recycle feed, the configuration in
FIG. 14 allows for an increase in the amount of fuels and lubricant
base oil products formed from a feedstock 1405.
Additional Embodiments
Embodiment 1
[0149] A method for separating a lubricant boiling range feedstock,
comprising: passing a feedstock with an initial boiling point of at
least 200.degree. C. into a gap between a first surface and a
second surface in a thermal diffusion separator; performing thermal
diffusion separation by maintaining the feedstock in the gap with a
temperature differential between the first surface and the second
surface of at least 5.degree. C. for a residence time; withdrawing
a plurality of fractions from the thermal diffusion separator
including a first fraction, a second fraction, and a third
fraction, the first fraction having a first value for a first
property and a second value for a second property; and blending at
least a portion of the second fraction and at least a portion of
the third fraction to form a blended fraction, the blended fraction
having a third value for the first property that differs from the
first value by 2.5% or less and a fourth value for the second
property that differs from the second value by at least 5.0%.
Embodiment 2
[0150] The method of Embodiment 1, wherein the plurality of
fractions further comprises a fourth fraction, the fourth fraction
being withdrawn from the thermal diffusion separator at a location
between the first fraction and the third fraction.
Embodiment 3
[0151] The method of Embodiment 2, the method further comprising
blending at least a portion of the second fraction and at least a
portion of the third fraction to form a blended fraction, the
blended fraction having a second value for the first property that
differs from the first value by 2.5% or less, wherein a yield of
product corresponds to the second property, the yield of product
for a combination of the first fraction plus the blended fraction
being greater than a yield for a contiguous blend of fractions from
the plurality of fractions that has a value for the first property
that differs from the first value by 2.5% or less, and wherein
optionally the blended fraction excludes at least a portion of the
fourth fraction.
Embodiment 4
[0152] The method of any of the above embodiments, wherein the
plurality of fractions are withdrawn from the thermal diffusion
separator at a plurality of heights, the second fraction being
withdrawn at a height greater than a height for the first fraction
and optionally the third fraction being withdrawn at a height lower
than the height for the first fraction.
Embodiment 5
[0153] The method of any of the above embodiments, wherein the
first property is viscosity index, viscosity at 100.degree. C.,
viscosity at 40.degree. C., pour point, cloud point, weight
percentage of sulfur, weight percentage of nitrogen, or weight
percentage of aromatics.
Embodiment 6
[0154] The method of Embodiments 1, 2, 4, or 5, wherein the second
property is product volume, viscosity index, viscosity at
100.degree. C., viscosity at 40.degree. C., pour point, cloud
point, oxidation stability, deposit tendency, Noack volatility,
weight percentage of sulfur, weight percentage of nitrogen, or
weight percentage of aromatics.
Embodiment 7
[0155] The method of any of the above embodiments wherein the
blended fraction is a non-contiguous blended fraction.
Embodiment 8
[0156] The method of any of the above embodiments, wherein
maintaining the feedstock in the gap for a residence time comprises
flowing feedstock through the gap in a continuous manner, the
residence time corresponding to a time required for the feedstock
to flow across a length of the gap.
Embodiment 9
[0157] The method of any of the above embodiments, wherein the
feedstock is a lubricant boiling range feedstock with a T5 boiling
point of at least 350.degree. C. and a final boiling point of
600.degree. C. or less.
Embodiment 10
[0158] The method of any of the above embodiments, wherein the
feedstock is maintained in the gap in the presence of an electric
field, the electric field optionally being an electric field that
varies spatially.
Embodiment 11
[0159] A system for performing hydroprocessing comprising: a
separation volume formed by a first surface and a second surface
aligned to face each other and define a separation volume width of
the separation volume, the separation volume having a separation
volume height defined by a top surface and a bottom surface and a
separation volume length, the separation volume width being from
0.25 mm to 6.0 mm, the separation volume height being at least 0.25
m, and a ratio of the separation volume width to the separation
volume height being less than 500; one or more heating elements
configured to maintain the first surface at a temperature; one or
more first electrodes associated with the first surface and one or
more second electrodes associated with the second surface; an input
manifold in fluid communication with the separation volume; and a
plurality of output channels in fluid communication with the
separation volume, the plurality of output channels being at two or
more different heights relative to the height of the separation
volume.
Embodiment 12
[0160] The method of Embodiment 11, wherein the first surface and
the second surface are parallel planar surfaces or wherein the
first surface and the second surface define a closed path.
Embodiment 13
[0161] The method of Embodiments 11 or 12, further comprising one
or more additional heating elements to maintain the second surface
at a temperature.
Embodiment 14
[0162] The method of Embodiments 11, 12, or 13, wherein the first
surface comprises a surface of a non-reactive layer in thermal
contact with a bulk material, the non-reactive layer preferably
comprising polyethyl ether ketone.
Embodiment 15
[0163] The method of any of Embodiments 11-14, further comprising
at least one adjustable gasket, the separation volume width being
determined based on a width of the at least one adjustable
gasket.
[0164] 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.
[0165] 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.
[0166] 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.
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