U.S. patent application number 14/101842 was filed with the patent office on 2015-06-11 for methods and systems for deoxygenating biomass-derived pyrolysis oil with a recycle column.
This patent application is currently assigned to UOP LLC. The applicant listed for this patent is UOP LLC. Invention is credited to Lance Awender Baird, Timothy A. Brandvold, Praneeth Dayanthe Edirisinghe.
Application Number | 20150159093 14/101842 |
Document ID | / |
Family ID | 53270522 |
Filed Date | 2015-06-11 |
United States Patent
Application |
20150159093 |
Kind Code |
A1 |
Baird; Lance Awender ; et
al. |
June 11, 2015 |
METHODS AND SYSTEMS FOR DEOXYGENATING BIOMASS-DERIVED PYROLYSIS OIL
WITH A RECYCLE COLUMN
Abstract
Methods and systems for deoxygenating a biomass-derived
pyrolysis oil are provided. An exemplary method includes combining
a biomass-derived pyrolysis oil stream with a heated low-molecular
weight fraction low-oxygen-pyoil diluent recycle stream to form a
heated diluted pyoil feed stream, which is contacted with a first
deoxygenating catalyst in the presence of hydrogen at first
hydroprocessing conditions effective to form a low-oxygen
biomass-derived pyrolysis oil effluent. A low-molecular weight
fraction low-oxygen-pyoil diluent recycle stream is formed by
contacting the low-oxygen biomass-derived pyrolysis oil effluent
with a fractionation column to separate a low molecular weight
fraction low-oxygen-pyoil diluent recycle stream at a cutpoint of
about 225.degree. C. or less. The low-molecular weight fraction
low-oxygen-pyoil diluent recycle stream is then heated prior to
combination with the biomass-derived pyrolysis oil stream.
Inventors: |
Baird; Lance Awender;
(Prospect Heights, IL) ; Brandvold; Timothy A.;
(Arlington Heights, IL) ; Edirisinghe; Praneeth
Dayanthe; (Chicago, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UOP LLC |
Des Plaines |
IL |
US |
|
|
Assignee: |
UOP LLC
Des Plaines
IL
|
Family ID: |
53270522 |
Appl. No.: |
14/101842 |
Filed: |
December 10, 2013 |
Current U.S.
Class: |
585/639 ;
422/187 |
Current CPC
Class: |
C10G 33/00 20130101;
C10G 3/50 20130101; Y02P 30/20 20151101 |
International
Class: |
C10G 3/00 20060101
C10G003/00 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] This invention was made with Government support under
DE-EE0002879 awarded by the U.S. Department of Energy. The
Government has certain rights in this invention.
Claims
1. A method for deoxygenating a biomass-derived pyrolysis oil, the
method comprising the steps of: combining a biomass-derived
pyrolysis oil stream with a heated low molecular weight fraction
low-oxygen-pyoil diluent recycle stream to form a heated diluted
pyoil feed stream that has a feed temperature of about 150.degree.
C. or greater; contacting the heated diluted pyoil feed stream with
a first deoxygenating catalyst in the presence of hydrogen at first
hydroprocessing conditions effective to form a low-oxygen
biomass-derived pyrolysis oil effluent; separating the low-oxygen
biomass-derived pyrolysis oil effluent to produce a low molecular
weight fraction low-oxygen-pyoil diluent recycle stream, wherein
the low molecular weight fraction low-oxygen-pyoil diluent recycle
stream is separated from the low-oxygen biomass-derived pyrolysis
oil effluent at a cutpoint of about 225.degree. C. or less; and
heating the low molecular weight fraction low-oxygen-pyoil diluent
recycle stream to form the heated low molecular weight fraction
low-oxygen-pyoil diluent recycle stream.
2. The method of claim 1, wherein the low molecular weight fraction
low-oxygen-pyoil diluent recycle stream is separated from the
low-oxygen biomass-derived pyrolysis oil effluent at a cutpoint of
between about 190 to about 225.degree. C.
3. The method of claim 1, wherein the first hydroprocessing
conditions include a reaction temperature of about the feed
temperature.
4. The method of claim 1, wherein heating the low molecular weight
fraction low-oxygen-pyoil diluent recycle stream comprises heating
to a temperature of from about 200 to about 450.degree. C.
5. The method of claim 1, wherein the biomass-derived pyrolysis oil
stream is combined with the heated low molecular weight fraction
low-oxygen-pyoil diluent recycle stream at a predetermined recycle
ratio of at least about 2:1; wherein the predetermined recycle
ratio is defined by a recycle mass flow rate of the heated low
molecular weight fraction low-oxygen-pyoil diluent recycle stream
to a pyoil mass flow rate of the biomass-derived pyrolysis oil
stream.
6. The method of claim 5, wherein the predetermined recycle ratio
is from about 2:1 to about 20:1.
7. The method of claim 1, wherein contacting the heated diluted
pyoil feed stream with the first deoxygenating catalyst comprises
partially deoxygenating the heated diluted pyoil feed stream, and
wherein the low-oxygen biomass-derived pyrolysis oil effluent
comprises a hydroprocessed organic phase that has a residual oxygen
content of from about 15 to about 25 wt. % of the hydroprocessed
organic phase.
8. The method of claim 1, further comprising subjecting the
low-oxygen biomass-derived pyrolysis oil effluent to a phase
separation to at least reduce an amount of water in the low-oxygen
biomass-derived pyrolysis oil effluent prior to separation of the
low molecular weight fraction low-oxygen-pyoil diluent recycle
stream.
9. The method of claim 8, wherein the low-oxygen biomass-derived
pyrolysis oil effluent is subjected to the phase separation at a
temperature of about 0 to 60.degree. C.
10. The method of claim 1, further comprising subjecting the low
molecular weight fraction low-oxygen-pyoil diluent recycle stream
to a phase separation to at least reduce an amount of water in the
low molecular weight fraction low-oxygen-pyoil diluent recycle
stream prior to heating and combining with the biomass-derived
pyrolysis oil stream.
11. The method of claim 10, wherein the low molecular weight
fraction low-oxygen-pyoil diluent recycle stream is subjected to
the phase separation at a temperature of about 60 to 140.degree.
C.
12. A method for deoxygenating a biomass-derived pyrolysis oil, the
method comprising the steps of: combining a biomass-derived
pyrolysis oil stream with a heated low molecular weight fraction
low-oxygen-pyoil diluent recycle stream to form a heated diluted
pyoil feed stream that has a feed temperature of about 150.degree.
C. or greater; contacting the heated diluted pyoil feed stream with
a first deoxygenating catalyst in the presence of hydrogen at first
hydroprocessing conditions effective to form a low-oxygen
biomass-derived pyrolysis oil effluent; contacting the low-oxygen
biomass-derived pyrolysis oil effluent with a fractionation column
to separate the low-oxygen biomass-derived pyrolysis oil effluent
into a low molecular weight fraction and a high molecular weight
fraction, wherein the low molecular weight fraction and high
molecular weight fraction are separated at a cutpoint of about
225.degree. C. or less, and wherein at least a portion of the a low
molecular weight fraction is routed for use as a low molecular
weight fraction low-oxygen-pyoil diluent recycle stream; separating
the low-oxygen biomass-derived pyrolysis oil effluent to produce a
low molecular weight fraction low-oxygen-pyoil diluent recycle
stream and a high molecular weight fraction of the low-oxygen
biomass-derived pyrolysis oil effluent, wherein the low molecular
weight fraction low-oxygen-pyoil diluent recycle stream and high
molecular weight fraction of the low-oxygen biomass-derived
pyrolysis oil effluent are separated at a cutpoint of about
225.degree. C. or less; heating the low molecular weight fraction
low-oxygen-pyoil diluent recycle stream to form the heated low
molecular weight fraction low-oxygen-pyoil diluent recycle stream;
and contacting the high molecular weight fraction of the low-oxygen
biomass-derived pyrolysis oil effluent with a second deoxygenating
catalyst in the presence of hydrogen at second hydroprocessing
conditions effective to form an ultralow-oxygen biomass-derived
pyrolysis oil effluent.
13. The method of claim 12, wherein the low molecular weight
fraction low-oxygen-pyoil diluent recycle stream is separated from
the low-oxygen biomass-derived pyrolysis oil effluent at a cutpoint
of between about 190 to about 225.degree. C.
14. The method of claim 12, wherein the first hydroprocessing
conditions include a reaction temperature of about the feed
temperature.
15. The method of claim 12, wherein heating the low molecular
weight fraction low-oxygen-pyoil diluent recycle stream comprises
heating to a temperature of from about 200 to about 450.degree.
C.
16. The method of claim 12, wherein the biomass-derived pyrolysis
oil stream is combined with the heated low molecular weight
fraction low-oxygen-pyoil diluent recycle stream at a predetermined
recycle ratio of at least about 2:1; wherein the predetermined
recycle ratio is defined by a recycle mass flow rate of the heated
low molecular weight fraction low-oxygen-pyoil diluent recycle
stream to a pyoil mass flow rate of the biomass-derived pyrolysis
oil stream.
17. The method of claim 12, wherein contacting the heated diluted
pyoil feed stream with the first deoxygenating catalyst comprises
partially deoxygenating the heated diluted pyoil feed stream, and
wherein the low-oxygen biomass-derived pyrolysis oil effluent
comprises a hydroprocessed organic phase that has a residual oxygen
content of from about 15 to about 25 wt. % of the hydroprocessed
organic phase.
18. The method of claim 12, further comprising subjecting the
low-oxygen biomass-derived pyrolysis oil effluent to a phase
separation to at least reduce an amount of water in the low-oxygen
biomass-derived pyrolysis oil effluent prior to separation of the
low molecular weight fraction low-oxygen-pyoil diluent recycle
stream.
19. The method of claim 12, further comprising subjecting the low
molecular weight fraction low-oxygen-pyoil diluent recycle stream
to a phase separation to at least reduce an amount of water in the
low molecular weight fraction low-oxygen-pyoil diluent recycle
stream prior to heating and combining with the biomass-derived
pyrolysis oil stream.
20. A system for deoxygenating a biomass-derived pyrolysis oil, the
system comprising: a first hydroprocessing reactor configured to
contain a first hydroprocessing catalyst, the first hydroprocessing
reactor configured to receive a heated diluted pyoil feed stream
and contact the heated diluted pyoil feed stream with the first
hydroprocessing catalyst in the presence of hydrogen under first
hydroprocessing conditions effective to form a low-oxygen
biomass-derived pyrolysis oil effluent, wherein the heated diluted
pyoil feed stream comprises a combination of a biomass-derived
pyrolysis oil stream and a heated low molecular weight fraction
low-oxygen-pyoil diluent recycle stream combined at a predetermined
ratio; a fractionation column configured to receive the low-oxygen
biomass-derived pyrolysis oil effluent and operate under conditions
such that a low molecular weight fraction low-oxygen-pyoil diluent
recycle stream is separated from the low-oxygen biomass-derived
pyrolysis oil effluent at a cutpoint of about 225.degree. C. or
lower; and a heater configured to receive and heat the low
molecular weight fraction low-oxygen-pyoil diluent recycle stream
to form the heated low molecular weight fraction low-oxygen-pyoil
diluent recycle stream.
Description
TECHNICAL FIELD
[0002] The technical field generally relates to methods and systems
for producing biofuels, and more particularly relates to methods
and systems for producing low-oxygen biomass-derived pyrolysis oil
from the catalytic deoxygenation of biomass-derived pyrolysis
oil.
BACKGROUND
[0003] Fast pyrolysis is a process during which organic
carbonaceous biomass feedstock, i.e., "biomass", such as wood
waste, agricultural waste, algae, etc., is rapidly heated to
between about 300.degree. C. to about 900.degree. C. in the absence
of air using a pyrolysis reactor. Under these conditions, solid
products, liquid products, and gaseous pyrolysis products are
produced. A condensable portion (vapors) of the gaseous pyrolysis
products is condensed into biomass-derived pyrolysis oil (commonly
referred to as "pyoil"). Biomass-derived pyrolysis oil can be
burned directly as fuel for certain boiler and furnace
applications, and can also serve as a potential feedstock in
catalytic processes for the production of fuels in petroleum
refineries. Biomass-derived pyrolysis oil has the potential to
replace up to 60% of transportation fuels, thereby reducing the
dependency on conventional petroleum and reducing its environmental
impact.
[0004] However, biomass-derived pyrolysis oil is a complex, highly
oxygenated organic liquid having properties that currently limit
its utilization as a biofuel. For example, biomass-derived
pyrolysis oil has high acidity and a low energy density
attributable in large part to oxygenated hydrocarbons in the oil,
which can undergo secondary reactions during storage particularly
if the oil is stored at elevated temperatures. As used herein,
"oxygenated hydrocarbons" or "oxygenates" are organic compounds
containing hydrogen, carbon, and oxygen. Such oxygenated
hydrocarbons in the biomass-derived pyrolysis oil include
carboxylic acids, phenols, cresols, alcohols, aldehydes, etc.
Conventional biomass-derived pyrolysis oil comprises about 30% or
greater by weight oxygen from these oxygenated hydrocarbons.
Conversion of biomass-derived pyrolysis oil into biofuels and
chemicals requires full or partial deoxygenation of the
biomass-derived pyrolysis oil. Such deoxygenation may proceed via
two main routes, namely the elimination of either water or
CO.sub.2. Unfortunately, deoxygenating biomass-derived pyrolysis
oil leads to rapid plugging or fouling of the processing catalyst
in a hydroprocessing reactor caused by the formation of solids from
the biomass-derived pyrolysis oil. Components in the pyrolysis oil
form on the processing catalysts causing catalytic bed fouling,
reducing activity of the catalyst, and causing build up in the
hydroprocessing reactor. It is believed that this plugging is due
to an acid catalyzed polymerization of the various components of
the biomass-derived pyrolysis oil, e.g., second order reactions in
which the various components of the oil polymerize with themselves,
that create either a glassy brown polymer or powdery brown char
that limits run duration and processability of the biomass-derived
pyrolysis oil. So far, improvements in reactor design and
processing methods (such as those described, e.g., in U.S. Pub. No.
2013/0152424) have delayed but not eliminated eventual plugging or
fouling the processing catalyst.
[0005] Accordingly, it is desirable to provide methods for
producing a low-oxygen biomass-derived pyrolysis oil without
plugging, or at least with further reduced plugging, of the
catalyst, thereby increasing run duration and improving
processability of the biomass-derived pyrolysis oil. Furthermore,
other desirable features and characteristics of the present
invention will become apparent from the subsequent detailed
description and the appended claims, taken in conjunction with the
accompanying drawings and this background.
BRIEF SUMMARY
[0006] Methods for deoxygenating a biomass-derived pyrolysis oil
are provided herein. In accordance with an exemplary embodiment, a
method for deoxygenating a biomass-derived pyrolysis oil comprises
the steps of: combining a biomass-derived pyrolysis oil stream with
a heated low molecular weight fraction low-oxygen-pyoil diluent
recycle stream to form a heated diluted pyoil feed stream that has
a feed temperature of about 150.degree. C. or greater; contacting
the heated diluted pyoil feed stream with a first deoxygenating
catalyst in the presence of hydrogen at first hydroprocessing
conditions effective to form a low-oxygen biomass-derived pyrolysis
oil effluent; contacting the low-oxygen biomass-derived pyrolysis
oil effluent with a fractionation column to separate a low
molecular weight fraction low-oxygen-pyoil diluent recycle stream;
and heating the low molecular weight fraction low-oxygen-pyoil
diluent recycle stream to form the heated low molecular weight
fraction low-oxygen-pyoil diluent recycle stream. In this
embodiment, the low molecular weight fraction low-oxygen-pyoil
diluent recycle stream is separated at a cutpoint of about
225.degree. C. or less.
[0007] Further, systems for deoxygenating a biomass-derived
pyrolysis oil are provided herein. In an exemplary embodiment, a
system comprises a first hydroprocessing reactor comprising a first
hydroprocessing catalyst. The first hydroprocessing reactor is
configured to receive a heated diluted pyoil feed stream and
operated under first hydroprocessing conditions effective to form a
low-oxygen biomass-derived pyrolysis oil effluent when the heated
diluted pyoil feed stream contacts the first hydroprocessing
catalyst in the presence of hydrogen, wherein the heated diluted
pyoil feed stream comprises a combination of a biomass-derived
pyrolysis oil and a heated low molecular weight fraction
low-oxygen-pyoil diluent recycle stream combined at a predetermined
ratio. The system further comprises a fractionation column
configured to receive the low-oxygen biomass-derived pyrolysis oil
effluent. The fractionation column is operated under conditions
such that a low molecular weight fraction low-oxygen-pyoil diluent
recycle stream is separated from the low-oxygen biomass-derived
pyrolysis oil effluent at a cutpoint of about 225.degree. C. or
lower. The system further comprises a heater configured to receive
and heat the low molecular weight fraction low-oxygen-pyoil diluent
recycle stream to form the heated low molecular weight fraction
low-oxygen-pyoil diluent recycle stream.
DETAILED DESCRIPTION OF THE DRAWINGS
[0008] The various embodiments will hereinafter be described in
conjunction with the following drawing figures, wherein like
numerals denote like elements, and wherein:
[0009] FIG. 1 is a block diagram illustrating a system and method
for deoxygenating a biomass-derived pyrolysis oil in accordance
with a first exemplary embodiment.
[0010] FIG. 2 is a block diagram illustrating a system and method
for deoxygenating a biomass-derived pyrolysis oil in accordance
with a second exemplary embodiment.
[0011] FIG. 3 is a block diagram illustrating a system and method
for deoxygenating a biomass-derived pyrolysis oil in accordance
with a third exemplary embodiment.
[0012] FIG. 4 is a block diagram illustrating a system and method
for deoxygenating a biomass-derived pyrolysis oil in accordance
with a fourth exemplary embodiment.
DETAILED DESCRIPTION
[0013] The following detailed description is merely exemplary in
nature and is not intended to limit the various embodiments or the
application and uses thereof. Furthermore, there is no intention to
be bound by any theory presented in the preceding background or the
following detailed description.
[0014] Various embodiments contemplated herein relate to methods
and systems for deoxygenating a biomass-derived pyrolysis oil. The
exemplary embodiments taught herein produce a low-oxygen
biomass-derived pyrolysis oil effluent by contacting a heated
diluted pyoil feed stream with a deoxygenating catalyst in the
presence of hydrogen at hydroprocessing conditions to partially
deoxygenate the heated diluted pyoil feed stream. It should be
appreciated that, while the deoxygenated oil produced according to
exemplary embodiments are generally described herein as a
"low-oxygen biomass-derived pyrolysis oil" or an "ultralow-oxygen
biomass-derived pyrolysis oil," these terms generally include any
pyoil produced having a lower oxygen concentration (i.e., a lower
residual oxygen content) than conventional biomass-derived
pyrolysis oil. The term "low-oxygen biomass-derived pyrolysis oil"
is pyoil having some oxygen, i.e., a biomass-derived pyrolysis oil
in which a portion of the oxygenated hydrocarbons have been
converted into hydrocarbons (i.e., a "hydrocarbon product"). In an
exemplary embodiment, the low-oxygen biomass-derived pyrolysis oil
comprises an organic phase (i.e. oil comprising primarily
oxygenates and/or hydrocarbons) that comprises oxygen in an amount
of from about 5 to about 25 weight percent (wt. %) of the organic
phase. The term "ultralow-oxygen biomass-derived pyrolysis oil" is
pyoil that has less oxygen than the low-oxygen biomass-derived
pyrolysis oil and includes pyoil having substantially no oxygen,
i.e., a biomass-derived pyrolysis oil in which substantially all
the oxygenated hydrocarbons have been converted into hydrocarbons
(i.e., a "hydrocarbon product"). In an exemplary embodiment, the
ultralow-oxygen biomass-derived pyrolysis oil comprises an organic
phase that comprises oxygen in an amount of from about 0 to about 2
wt. % of the organic phase. "Hydrocarbons" as used herein are
organic compounds that contain principally only hydrogen and
carbon, i.e., oxygen-free.
[0015] A heated diluted pyoil feed stream may be formed by
combining a biomass-derived pyrolysis oil stream with a heated
low-oxygen-pyoil diluent recycle stream. The heated
low-oxygen-pyoil diluent recycle stream is formed from a portion of
the low-oxygen biomass-derived pyrolysis oil effluent that has been
recycled and heated. Therefore, the heated low-oxygen-pyoil diluent
recycle stream has already been partially deoxygenated, which
removes not only some of the oxygen but also significantly reduces
the amount of pyoil reactant components that can undergo secondary
polymerization reactions with various constituents of the
biomass-derived pyrolysis oil stream.
[0016] The heated diluted pyoil feed stream is formed upstream from
a hydroprocessing reactor that contains a deoxygenating catalyst in
the presence of hydrogen and that is operating at hydroprocessing
conditions. The heated diluted pyoil feed stream is introduced to
the hydroprocessing reactor and contacts the deoxygenating catalyst
to form the low-oxygen biomass-derived pyrolysis oil effluent.
[0017] While combining a heated portion of the low-oxygen pyoil
diluent recycle stream with the biomass-derived pyrolysis oil
stream is effective for reducing the formation of secondary
polymerization solids, it has been found that the recycled pyoil
diluent stream can still react with the biomass-derived pyrolysis
oil stream. In fact, over time the molecular weight and viscosity
of the resulting low-oxygen biomass-derived pyrolysis oil effluent
can increase to such an extent that the heated diluted pyoil feed
stream can no longer be processed in a fixed bed reactor due to an
increase in differential pressure across the reactor.
[0018] Without wishing to be bound by theory, it is believed that
certain compounds in the low-oxygen pyoil diluent recycle stream
may undergo secondary polymerization reactions in the
biomass-derived pyrolysis oil stream resulting in a gradual
increase in molecular weight and viscosity of the effluent, which
ultimately limits the time on stream before a pressure differential
across the reactor becomes too high. Described herein are methods,
systems, and apparatus that reduce or eliminate these secondary
polymerization reactions by removing or reducing higher molecular
weight species from the low-oxygen pyoil diluent recycle stream
prior to combination of the recycle stream with the biomass-derived
pyrolysis oil stream.
[0019] As used herein, the phrase "low molecular weight species" as
it relates to chemical species found in the low-oxygen pyoil
diluent recycle stream refers to the chemical species that
evaporate and are collected as vapor as a result of fractional
distillation of the low-oxygen pyoil diluent recycle stream to a
desired cutpoint. Conversely, the phrase "high molecular weight
species" as it relates to chemical species found in the low-oxygen
pyoil diluent recycle stream refers to the chemical species that
remain liquid following this distillation. In some embodiments, the
desired cutpoint is a temperature of about 225.degree. C. or less;
such as between about 190 to about 225.degree. C.; such as between
about 200 to about 220.degree. C.; such as about 215.degree. C.
[0020] Thus, in some embodiments, the low-oxygen pyoil diluent
recycle stream is subjected to a distillation and the low molecular
weight fraction collected to a cutpoint of between about 190 to
about 225.degree. C. is routed for optional further processing
prior to combination with a biomass-derived pyrolysis oil stream.
The cutpoint is selected such that the remaining high molecular
weight fraction has a liquid viscosity low enough to be
processable, e.g., in a second hydroprocessing reactor.
[0021] Thus, in an exemplary embodiment a biomass-derived pyrolysis
oil stream has an initial temperature of about 100.degree. C. or
less, for example of about ambient, prior to being combined with a
heated low molecular weight fraction low-oxygen-pyoil diluent
recycle stream to form a heated diluted pyoil feed stream. The low
molecular weight fraction is heated to a recycle temperature of
about 200 to about 450.degree. C. before being combined with the
biomass-derived pyrolysis oil stream at a predetermined recycle
ratio of at least about 2:1 diluent recycle stream:pyrolysis oil
stream. In some embodiments, the biomass-derived pyrolysis oil
stream is diluted at a ratio of between about 2:1 to about 20:1
diluent recycle stream:pyrolysis oil stream. By combining the
biomass-derived pyrolysis oil stream with the heated low molecular
weight fraction low-oxygen-pyoil diluent recycle stream, the
biomass-derived pyrolysis oil stream is diluted by the low
molecular weight fraction and is rapidly heated, for example, to a
temperature that is suitable for hydroprocessing. Moreover,
diluting the biomass-derived pyrolysis oil stream with the mutually
miscible heated diluent facilitates solubilizing any solids that
may have formed during storage or that could otherwise form in the
pyoil during subsequent hydroprocessing (e.g. glassy brown polymers
or powdery brown char).
[0022] Further, it has been found that limiting the conversion per
pass across the first hydroprocessing reactor to retain a portion
of the initial oxygen in the low-oxygen biomass-derived pyrolysis
oil effluent facilitates separation of the low and high molecular
weight fractions, while still being sufficiently converted such
that the portion of the effluent that is not recycled may still be
fully deoxygenated by a second stage of hydroprocessing, e.g., with
a second hydroprocessing reactor. As such, in some embodiments, the
hydroprocessing conditions utilized in the first reactor are such
that the conversion per pass is limited so that between about 10 to
25% residual oxygen, such as between about 15 to 22 wt. % residual
oxygen, such as about 20 wt. % residual oxygen, is retained in the
hydroprocessed organic phase of the low-oxygen biomass-derived
pyrolysis oil effluent.
[0023] It has further been found that the amount of residual water
that remains in the low molecular weight fraction low-oxygen pyoil
diluent recycle stream affects the extent of secondary
polymerization reactions between components of the recycled diluent
stream and components of the biomass-derived pyrolysis oil stream.
Thus, in some embodiments, the amount of water in the low molecular
weight fraction low-oxygen pyoil diluent recycle stream may be
modulated to further inhibit the secondary polymerization
reactions. The amount of water in the low molecular weight fraction
low-oxygen pyoil diluent recycle stream may be adjusted by any
suitable method, such as by incorporation of one or more optional
sub-systems to the recycle system.
[0024] For instance, in some embodiments the low-oxygen pyoil
diluent recycle stream may be subjected to phase separation prior
to fractional distillation such that the low-oxygen pyoil diluent
recycle stream is separated into a H.sub.2 gas containing stream, a
water stream, and a water-depleted low-oxygen-pyoil stream. If
phase separation is used, the H.sub.2 gas containing stream and
water stream are diverted and collected, while the water-depleted
low-oxygen-pyoil stream is subjected to fractional distillation to
separate low molecular weight and high molecular weight fractions,
as described above.
[0025] Before phase separation, the low-oxygen pyoil diluent
recycle stream typically contains about 10 wt. % water. However,
the temperature at which the low-oxygen pyoil diluent recycle
stream is subjected to phase separation affects the solubility of
water in the low-oxygen pyoil diluent recycle stream, and thus the
amount of residual water that remains in the water-depleted
low-oxygen-pyoil stream after phase separation. Thus, in some
embodiments, the temperature of the low-oxygen pyoil diluent
recycle stream may be adjusted (e.g. cooled by any suitable means,
such as with a condenser) after exiting the first hydroprocessing
reactor and before phase separation.
[0026] In some embodiments, the temperature of the low-oxygen pyoil
diluent recycle stream may be adjusted so that the amount of
residual water that remains in the water-depleted low-oxygen-pyoil
stream after phase separation is minimized. In such embodiments,
the temperature of the low-oxygen pyoil diluent recycle stream may
be adjusted so that phase separation is conducted within the
temperature range of about 0 to 60.degree. C., such as between
about 30 to 60.degree. C.
[0027] In some alternative embodiments, the temperature of the of
the low-oxygen pyoil diluent recycle stream may be adjusted so that
the amount of residual water that remains in the water-depleted
low-oxygen-pyoil stream after phase separation is maximized. That
is, the temperature of the low-oxygen pyoil diluent recycle stream
may be adjusted such that water and organic phases of the
low-oxygen pyoil diluent recycle stream are fully miscible as the
recycle stream enters the separator. In these embodiments, only two
streams will result from phase separation: a H.sub.2 gas containing
stream, and a H.sub.2 gas depleted low-oxygen-pyoil liquid stream.
In such embodiments, the temperature of the low-oxygen pyoil
diluent recycle stream may be adjusted so that phase separation is
conducted within the temperature range of about 140 to 200.degree.
C.
[0028] In yet further alternative embodiments, the temperature of
the low-oxygen pyoil diluent recycle stream may be adjusted so that
the amount of residual water that remains in the water-depleted
low-oxygen-pyoil stream after phase separation is at an amount
between the minimum and maximum possible amounts. In such
embodiments, the temperature of the low-oxygen pyoil diluent
recycle stream may be adjusted so that phase separation is
conducted within the temperature range of about 60 to 140.degree.
C.
[0029] In addition or in the alternative, the amount of water in
the low-oxygen pyoil diluent recycle stream may be adjusted after
fractional distillation and prior to combination with the
biomass-derived pyrolysis oil stream. As described above with
respect to the low-oxygen pyoil diluent recycle stream, the
temperature of the low molecular weight fraction low-oxygen pyoil
diluent recycle stream affects the saturation point of water vapor,
and thus, the amount of residual water that remains in the low
molecular weight fraction low-oxygen pyoil diluent recycle stream
after distillation. Thus, in some embodiments, the temperature of
the low molecular weight fraction low-oxygen pyoil diluent recycle
stream may be adjusted (e.g. cooled by any suitable means, such as
with a condenser) after distillation to form aqueous and organic
phases. In such embodiments, the aqueous phase may then be
separated, e.g., with a phase separator, and the organic phase
routed for combination with the biomass-derived pyrolysis oil
stream.
[0030] For instance, in some embodiments the temperature of the low
molecular weight fraction low-oxygen pyoil diluent recycle stream
may be adjusted so as create an aqueous phase and an organic phase
with a minimum amount of residual water. The aqueous phase may then
be separated, e.g., with a phase separator, and the organic phase
routed for combination with the biomass-derived pyrolysis oil
stream. In such embodiments, the temperature of the low molecular
weight fraction low-oxygen pyoil diluent recycle stream may be
adjusted so that phase separation is conducted within the
temperature range of about 0 to 60.degree. C., such as between
about 10 to 50.degree. C.
[0031] In some alternate embodiments, the temperature of the low
molecular weight fraction of the low-oxygen pyoil diluent recycle
stream may be adjusted so that the amount of residual water that
remains in the low molecular weight fraction low-oxygen pyoil
diluent recycle stream is maximized. In such embodiments, the
temperature of the low molecular weight fraction low-oxygen pyoil
diluent recycle stream may be adjusted such that the residual water
in the low molecular weight fraction low-oxygen pyoil diluent
recycle stream after distillation is completely miscible. That is,
in these embodiments, the temperature of the low molecular weight
fraction low-oxygen pyoil diluent recycle stream after distillation
may be adjusted such that the low molecular weight fraction
low-oxygen pyoil diluent recycle stream is a single phase. In these
embodiments, the temperature of the low molecular weight fraction
low-oxygen pyoil diluent recycle stream after distillation may be
adjusted to be within the range of about 140 to 200.degree. C.
after distillation but prior to combination with the
biomass-derived pyrolysis oil stream. In such embodiments, the low
molecular weight fraction low-oxygen pyoil diluent recycle stream
may not be subjected to a phase separation prior to combination
with the biomass-derived pyrolysis oil stream.
[0032] In yet further alternative embodiments, the temperature of
the low molecular weight fraction low-oxygen pyoil diluent recycle
stream may be adjusted so that the amount of residual water that
remains in the low molecular weight fraction low-oxygen pyoil
diluent recycle stream is at an amount between the minimum and
maximum possible amounts. The aqueous phase may then be separated,
e.g., with a phase separator, and the organic phase routed for
combination with the biomass-derived pyrolysis oil stream. In such
embodiments, the temperature of the low molecular weight fraction
low-oxygen pyoil diluent recycle stream may be adjusted so that
phase separation is conducted within the temperature range of about
60 to 150.degree. C., such as between about 60 to 140.degree.
C.
[0033] Four specific exemplary embodiments are described below with
reference to FIGS. 1-4. Discussion of these embodiments is not
intended to be limiting, but rather merely illustrative of systems
and apparatus that can be used to achieve the process features
described above.
[0034] Referring to FIG. 1, a schematic depiction of a system 10
for deoxygenating a biomass-derived pyrolysis oil in accordance
with an exemplary embodiment is provided. As illustrated, a
biomass-derived pyrolysis oil stream 12 is introduced to the
apparatus 10. The biomass-derived pyrolysis oil found in the
biomass-derived pyrolysis oil stream 12 may be produced, such as,
for example, from pyrolysis of biomass in a pyrolysis reactor.
Virtually any form of biomass can be used for pyrolysis to produce
the biomass-derived pyrolysis oil. The biomass-derived pyrolysis
oil may be derived from biomass material, such as, wood,
agricultural waste, nuts and seeds, algae, forestry residues, and
the like. The biomass-derived pyrolysis oil may be obtained by
different modes of pyrolysis, such as, for example, fast pyrolysis,
vacuum pyrolysis, catalytic pyrolysis, and slow pyrolysis or
carbonization, and the like.
[0035] The composition of the biomass-derived pyrolysis oil can
vary considerably and depends on the feedstock and processing
variables. Examples of biomass-derived pyrolysis oil "as-produced"
can contain up to about 1,000 to about 30,000 ppm total metals,
about 20 to about 33 weight percent (wt. %) of water that can have
high acidity (e.g. total acid number (TAN)>150), and a solids
content of from about 0.1 wt. % to about 5 wt. %. The
biomass-derived pyrolysis oil may be untreated (e.g. "as
produced"). However, if needed the biomass-derived pyrolysis oil
can be selectively treated to reduce any or all of the above to a
desired level. In an exemplary embodiment, the biomass-derived
pyrolysis oil comprises an organic phase (i.e., oil comprising
primarily oxygenates and/or hydrocarbons along with any dissolved
water) that has a residual oxygen content of about 10 wt. % or
greater, for example of about 30 wt. % or greater, for example from
about 30 to about 50 wt. %, such as from about 35 to about 45 wt. %
of the organic phase.
[0036] The biomass-derived pyrolysis oil may be thermally unstable
and may be stored and/or handled so as to reduce its exposure to
higher temperatures, thus minimizing secondary polymerization
reactions between various components in the biomass-derived
pyrolysis oil prior to hydroprocessing. In an exemplary embodiment,
the biomass-derived pyrolysis oil stream 12 has as an initial
temperature (e.g. storage temperature) of about 100.degree. C. or
less, for example from about 15.degree. C. to about 100.degree. C.,
for example from about 15.degree. C. to about 50.degree. C., such
as about ambient, to inhibit secondary polymerization
reactions.
[0037] Upstream from a first hydroprocessing reactor 18, the
biomass-derived pyrolysis oil stream 12 is combined and diluted
with a heated low molecular weight fraction low-oxygen-pyoil
diluent recycle stream 14 to form a heated diluted pyoil feed
stream 16. The heated low-molecular weight fraction 14 can be
introduced to the biomass-derived pyrolysis oil stream 12 in a
single stream together with a H.sub.2-containing gas stream 33, as
illustrated and discussed in further detail below, or
alternatively, the heated low-molecular weight fraction 14 can be
introduced to the biomass-derived pyrolysis oil stream 12 in a
single or in multiple separate streams that do not include the
H.sub.2-containing gas stream 33. For example, the
H.sub.2-containing gas stream 33 can be introduced directly to the
heated diluted pyoil feed stream 16 and/or directly to the first
hydroprocessing reactor 18, and the heated low-molecular weight
fraction 14 can be introduced to the biomass-derived pyrolysis oil
stream 12 absent the hydrogen-containing gas stream 33.
[0038] As will be discussed in further detail below, the heated
low-molecular weight fraction 14 is a low-molecular weight fraction
of a pyoil stream that has been previously partially deoxygenated,
recycled, and heated. As such, the heated low-molecular weight
fraction 14 has less pyoil reactant components that can undergo
secondary polymerization reactions (which result in formation of
solids or a viscosity increase of the heated diluted pyoil feed
stream 16), and contains some oxygen but less oxygen than the
biomass-derived pyrolysis oil stream 12. By having some oxygen in
the heated low-molecular weight fraction 14, the biomass-derived
pyrolysis oil stream 12 and the heated low-molecular weight
fraction 14 are mutually miscible. Moreover, it has been found that
incomplete conversion (i.e., leaving some oxygen in the low-oxygen
biomass-derived pyrolysis oil effluent) facilitates separation of
the low and high molecular weight fractions, while still being
sufficiently converted such that the portion of the effluent that
is not recycled may still be fully deoxygenated by a second stage
of hydroprocessing, e.g., with a second hydroprocessing
reactor.
[0039] In an exemplary embodiment, the hydroprocessing conditions
utilized in the first reactor are such that the conversion per pass
is limited so that between about 10 to 25 wt. % oxygen, such as
between about 15 to 22 wt. % oxygen, such as about 20 wt. % oxygen,
is retained in the low-oxygen biomass-derived pyrolysis oil
effluent. In one example, the hydroprocessed organic phase
comprises oxygenates such as phenols, alkyl phenols, alcohols,
ethers, and/or the like that are similar to and/or easily
solubilize the oxygenates contained in the biomass-derived
pyrolysis oil stream 12.
[0040] In an exemplary embodiment, the heated low-molecular weight
fraction 14 has a temperature of from about 200 to about
450.degree. C., for example from about 300 to about 450.degree. C.,
such as from about 325 to about 425.degree. C. In an exemplary
embodiment, the biomass-derived pyrolysis oil stream 12 and the
heated low-molecular weight fraction 14 are combined at a
predetermined recycle ratio that is defined by a mass flow rate of
the heated low-molecular weight fraction 14 to a mass flow rate of
the biomass-derived pyrolysis oil stream 12 to form the heated
diluted pyoil feed stream 16 that has a feed temperature of about
150.degree. C. or greater, for example from about 150 to about
400.degree. C., such as from about 200 to about 350.degree. C. In
an exemplary embodiment, the biomass-derived pyrolysis oil stream
12 is combined with the heated low-molecular weight fraction 14 at
the predetermined recycle ratio of from about 2:1 to about
20:1.
[0041] The heated diluted pyoil feed stream 16 is introduced to the
first hydroprocessing reactor 18. The first hydroprocessing reactor
18 can be a continuous flow reactor, such as a fixed-bed reactor, a
continuous stirred tank reactor (CSTR), a trickle bed reactor, an
ebulliating bed reactor, a slurry reactor, or any other reactor
known to those skilled in the art for hydroprocessing.
[0042] The first hydroprocessing reactor 18 contains a
deoxygenating catalyst in the presence of hydrogen. In an exemplary
embodiment, the deoxygenating catalyst comprises a metal or a
combination of metals, such as a base metal(s), a refractory
metal(s), and/or a noble metal(s), such as platinum, palladium,
ruthenium, nickel, molybdenum, tungsten, and/or cobalt. The
metal(s) may be on a support, such as a carbon support, a silica
support, an alumina support, a silica-alumina support (amorphous or
zeolite), a gamma alumina support, a zirconia support, and/or a
titanium support. Other hydroprocessing catalysts known to those
skilled in the art may also be used.
[0043] The first hydroprocessing reactor 18 is operating at
hydroprocessing conditions. In an exemplary embodiment, the
hydroprocessing conditions include a reactor temperature of from
about 150 to about 400.degree. C., such as from about 200 to about
350.degree. C., a reactor pressure of from about 2 to about 20 MPa
gauge, a liquid hourly space velocity on a basis of weight of the
biomass-derived pyrolysis oil/weight of catalyst/hour (hr.sup.-1)
of from about 0.10 to about 1 hr.sup.-1, and a hydrogen-containing
gas treat rate of from about 1,000 to about 15,000 standard cubic
feet per barrel (SCF/B).
[0044] In an exemplary embodiment, the heated diluted pyoil feed
stream 16 is formed just upstream of the first hydroprocessing
reactor 18 and the feed temperature of the heated diluted pyoil
feed stream 16 is at about the reactor temperature to facilitate
rapid catalytic deoxygenation of the heated diluted pyoil feed
stream 16 with a short or minimal residence time. The term
"residence time" as used herein is the amount of time from when the
biomass-derived pyrolysis oil stream 12 is combined with the heated
low-molecular weight fraction 14 to when the heated diluted pyoil
feed stream 16 initially contacts the deoxygenating catalyst. By
having a relatively short residence time, less secondary
polymerization reactions can occur in the heated diluted pyoil feed
stream 16 at elevated temperatures before hydroprocessing begins.
In an exemplary embodiment, the residence time is about 60 seconds
or less, for example about 20 seconds or less, for example about 10
second or less, such as from about 10 seconds to about 1
second.
[0045] The heated diluted pyoil feed stream 16 contacts the
deoxygenating catalyst at the hydroprocessing conditions in the
presence of hydrogen and forms a low-oxygen biomass-derived
pyrolysis oil effluent 20 by converting a portion of the oxygenated
hydrocarbons in the biomass-derived pyrolysis oil into hydrocarbons
(i.e., partial deoxygenation). In particular, hydrogen from a
make-up hydrogen stream 31 is optionally combined with hydrogen 30
recovered from the low-oxygen biomass-derived pyrolysis oil
effluent 20 to form a hydrogen-containing gas stream 33. The
hydrogen-containing gas stream 33 removes oxygen from the
biomass-derived pyrolysis oil as water to produce the low-oxygen
biomass-derived pyrolysis oil effluent 20 that comprises an aqueous
phase and a hydroprocessed organic phase. The hydroprocessed
organic phase comprises oil that is partially deoxygenated with
some residual oxygenated hydrocarbons. In an exemplary embodiment,
the hydroprocessed organic phase of the low-oxygen biomass-derived
pyrolysis oil effluent 20 has a residual oxygen content of from
about 5 to about 30 wt. %, for example from about 10 to about 25
wt. %, such as from about 15 to about 25 wt. % of the
hydroprocessed organic phase.
[0046] It is believed that the benefits of catalytically
deoxygenating the biomass-derived pyrolysis oil that is diluted
with the heated low-molecular weight fraction 14, may result in
increasing hydrogen solubility, immolating the exotherm by dilution
of the reactive species in the biomass-derived pyrolysis oil stream
12, and reducing the reaction rate of bimolecular reactants that
lead to secondary polymerization reactions. As such, simple
reactions of the biomass-derived pyrolysis oil with hydrogen to
form a lower-oxygen biomass-derived pyrolysis oil dominate while
secondary polymerization reactions of biomass-derived pyrolysis oil
components with themselves are reduced or minimized, thereby
reducing or minimizing the formation of glassy brown polymers or
powdery brown char on the deoxygenating catalyst, as well as
reducing or minimizing viscosity increases in the heated diluted
pyoil feed stream 16 resulting from continued recycling of the
low-oxygen biomass-derived pyrolysis oil effluent 20.
[0047] In an exemplary embodiment, the low-oxygen biomass-derived
pyrolysis oil effluent 20 is removed from the first hydroprocessing
reactor 18, passed through a chiller 22, and subjected to a first
phase separation. In an exemplary embodiment, the chiller 22 cools
the low-oxygen biomass-derived pyrolysis oil effluent 20 to a
temperature of from about 30 to about 60.degree. C. The first phase
separation removes light volatiles, water, light liquids, and
solids (if present) from the low-oxygen biomass-derived pyrolysis
oil effluent 20 using one or more separation vessels, fractionation
columns, heaters, condensers exchangers, pipes, pumps, compressors,
controllers, and/or the like. In an exemplary embodiment and as
illustrated, the first phase separation is conducted with a high
pressure three-phase separator 24. The low-oxygen biomass-derived
pyrolysis oil effluent 20 is introduced to the high pressure
three-phase separator 24 and is separated into a water-containing
(i.e., aqueous) stream 26, a H.sub.2 gas-containing stream 30, and
a water-depleted low-oxygen-pyoil stream 36. The aqueous stream 26
is passed along to an aqueous-organic separation zone. The H.sub.2
gas-containing stream 30 may be removed from the apparatus 10, or
optionally a portion or all of the H.sub.2 gas-containing stream 30
is combined with a hydrogen from a make-up hydrogen stream 31 and
diverted to a compressor 32, which generates the H.sub.2-containing
gas stream 33 that may be introduced to the heated diluted pyoil
feed stream 16 and/or directly to the first hydroprocessing reactor
18, as described above.
[0048] The water-depleted low-oxygen-pyoil stream 36 is then
directed to a recycle column 38, where the water-depleted
low-oxygen-pyoil stream 36 is separated into low-molecular weight
and high-molecular weight fractions. In an exemplary embodiment,
the recycle column 38 is a fractionation column wherein a
low-molecular weight fraction 40 and a high-molecular weight
fraction 42 are separated at a cutpoint temperature of about
225.degree. C. or less, such as between about 190 to about
225.degree. C.; such as between about 200 to about 220.degree. C.;
such as about 215.degree. C.
[0049] The low-molecular weight fraction 40 is passed through a
chiller 44, and delivered to a phase separator 46, which separates
an organic volatile gas stream 48, an aqueous stream 50, and a
low-molecular weight fraction organic liquid phase 52. In one
embodiment, the organic volatile gas stream 48 and aqueous stream
50 are diverted and collected, while the low-molecular weight
fraction organic liquid phase 52 is passed through a pump 56 and
sent to a heater 34 to generate the heated low-molecular weight
fraction 14 discussed above. As indicated above, the heated
low-molecular weight fraction 14 is combined with the
biomass-derived pyrolysis oil stream 12, and is thus recycled
through the first hydroprocessing reactor 18. In some embodiments,
a portion of the low-molecular weight fraction organic liquid phase
52 is diverted prior to entering the heater 34 and instead directed
to be combined with the high-molecular weight fraction 42. In these
embodiments, the combination may then be directed to a second
hydroprocessing reactor system 28, as discussed below.
[0050] The high-molecular weight fraction 42 from the recycle
column 38 is passed through a pump 60 and is sent to a second
hydroprocessing reactor system 28 for further processing. The
second hydroprocessing reactor system 28 may be any suitable
hydroprocessing reactor system known in the art, and may include,
for instance, a batch reactor or continuous flow reactor, such as a
fixed-bed reactor, a continuous stirred tank reactor (CSTR), a
trickle bed reactor, an ebulliating bed reactor, a slurry reactor,
or any other reactor known to those skilled in the art for
hydroprocessing. The second hydroprocessing reactor system 28
contains a second hydroprocessing reactor that utilizes a
deoxygenating catalyst in the presence of hydrogen as discussed
above with respect to the deoxygenating catalyst in the first
hydroprocessing reactor 18. The second hydroprocessing reactor is
operated at hydroprocessing conditions. In an exemplary embodiment,
the hydroprocessing conditions include a second hydroprocessing
reactor temperature of from about 150 to about 500.degree. C., such
as from about 300 to about 450.degree. C., a reactor pressure of
from about 2 to about 20 MPa gauge, a liquid hourly space velocity
on a basis of weight of the biomass-derived pyrolysis oil/weight of
catalyst/hour (hr.sup.-1) of from about 0.1 to about 1.5 hr.sup.-1,
and a hydrogen-containing gas treat rate of from about 1,000 to
about 15,000 standard cubic feet per barrel (SCF/B). The
deoxygenating catalyst in the second hydroprocessing reactor system
28 can be the same as or different from the deoxygenating catalyst
in the first hydroprocessing reactor 18.
[0051] The second hydroprocessing reactor system 28 removes oxygen
from the net organic liquid product from the first stage
hydroprocessing reactor system (comprising the heavy and optionally
a portion of the light molecular weight fractions of the low-oxygen
biomass-derived pyrolysis oil) to produce ultralow-oxygen
biomass-derived pyrolysis oil effluent. The oil contained in the
ultralow-oxygen biomass-derived pyrolysis oil effluent may be
partially deoxygenated with some residual oxygenated hydrocarbons,
or may be substantially fully deoxygenated where substantially all
of the oxygenated hydrocarbons are converted into hydrocarbons. In
an exemplary embodiment, the ultralow-oxygen biomass-derived
pyrolysis oil effluent comprises a hydroprocessed organic phase
that has a residual oxygen content of about 2 wt. % or less, for
example from about 1 to about 0 wt. %, such as about 0.1 to about 0
wt. % of the hydroprocessed organic phase.
[0052] In other embodiments, the system 10 described above may
contain one or more additional optional elements at least for the
manipulation of temperature and/or water content in various pyoil
streams throughout the process.
[0053] For instance, in a second exemplary embodiment, the system
10 is as described above, but is further configured to provide
improved control of the temperature of the low-oxygen
biomass-derived pyrolysis oil effluent 20 when it is introduced to
the high pressure three-phase separator 24. An example of such an
embodiment is seen in FIG. 2.
[0054] Specifically, the outlet temperature of the chiller 22 may
be monitored with a temperature controller 64 and the temperature
and/or flow rate of coolant through the chiller 22 adjusted to
achieve a desired temperature of the chilled low-oxygen
biomass-derived pyrolysis oil effluent 20. Alternatively or in
addition, a portion of the low-oxygen biomass-derived pyrolysis oil
effluent 20 may be diverted around the chiller 22 to achieve a
desired temperature of the chilled low-oxygen biomass-derived
pyrolysis oil effluent 20. In this way, the temperature of the
low-oxygen biomass-derived pyrolysis oil effluent 20 can be
modulated to a greater extend prior to introducing the low-oxygen
biomass-derived pyrolysis oil effluent 20 into the high pressure
three-phase separator 24. This modulation provides a degree of
control of the amount of water that remains miscible in the
low-oxygen biomass-derived pyrolysis oil effluent 20 as it enters
the high pressure separator 24.
[0055] In a third exemplary embodiment, the system 10 is as
initially described, but is further configured to provide improved
control of the amount of residual water in the heated low-molecular
weight fraction 14 when it is combined with the biomass-derived
pyrolysis oil stream 12 and fed to the first hydroprocessing
reactor 18. An example of such an embodiment is seen in FIG. 3.
[0056] Specifically, the low-molecular weight fraction 40 exiting
the recycle column 38 is passed through the chiller 44 and the
phase separator 46 under conditions such that water content of the
reflux 70 is minimized Net water and organic portions 50 exiting
the phase separator 46 are directed to a pump 56 and passed through
a heater 66 where the temperature is increased such that an
additional portion or, in some cases, all of a separate water phase
present in the low-molecular weight fraction becomes miscible.
Specifically, the outlet temperature of the heater 66 may be
monitored with a temperature controller 68 and the temperature of
the heater 66 adjusted to achieve a desired temperature prior to
entering phase separator 72. Thus, in these embodiments, the phase
separator 46 separates the low-molecular weight fraction 40 into an
organic volatile gas stream 48, a low-molecular weight fraction
organic reflux liquid phase 70, and an organic/aqueous stream 50.
The organic volatile gas stream 48 is handled as described above
and the organic/aqueous phases in stream 50 are separated (if
desired) in phase separator 72.
[0057] Like the low-molecular weight fraction organic liquid phase
52 in the embodiments described above, the low-molecular weight
fraction organic/aqueous liquid phase 50 is then sent to a heater
34 to generate the heated low-molecular weight fraction 14
discussed above. In some embodiments, a portion of the
low-molecular weight fraction organic/aqueous liquid phase 50 is
diverted prior to entering the heater 34 and instead directed to be
combined with the high-molecular weight fraction 42, with the
combination directed to a second hydroprocessing reactor system 28,
as previously discussed.
[0058] In a fourth exemplary embodiment, the system 10 is as
initially described, but is further configured to provide improved
control of the temperature of the low-oxygen biomass-derived
pyrolysis oil effluent 20 as described in the second exemplary
embodiment, and provide improved control of the amount of residual
water in the heated low-molecular weight fraction 14 as described
in the third exemplary embodiment. An example of a fourth exemplary
embodiment is shown in FIG. 4. As seen in FIG. 4, the system 10 is
as initially described but further includes temperature controller
64 located downstream of the chiller 22 (as described in detail in
the second exemplary embodiment), and a heater 66, a temperature
controller 68, and a phase separator 72 (as described in detail in
the third exemplary embodiment).
[0059] Accordingly, methods for deoxygenating a biomass-derived
pyrolysis oil have been described. Unlike the prior art, the
exemplary embodiments taught herein produce a low-oxygen
biomass-derived pyrolysis oil effluent by contacting a heated
diluted pyoil feed stream with a deoxygenating catalyst in the
presence of hydrogen at hydroprocessing conditions. In particular,
the heated diluted pyoil feed stream is formed by combining a
biomass-derived pyrolysis oil stream with a heated low-molecular
weight fraction of a low-oxygen-pyoil diluent recycle stream. The
heated low-molecular weight fraction is formed from a portion of
the low-oxygen biomass-derived pyrolysis oil effluent that has been
separated in to at least low and high molecular weight fractions,
with at least a portion of the low molecular weight fraction
recycled and heated. The heated diluted pyoil feed stream is
introduced to a hydroprocessing reactor and contacts the
deoxygenating catalyst to partially deoxygenate the heated diluted
pyoil feed stream to form the low-oxygen biomass-derived pyrolysis
oil effluent. By contacting the deoxygenating catalyst with the
heated diluted pyoil feed stream in the presence of hydrogen at the
hydroprocessing conditions, the amount of glassy brown polymer or
powdery brown char formed on the deoxygenating catalyst is
substantially reduced or minimized relative to conventional
methods. Further, separation and recycling of only the low
molecular weight fraction of the low-oxygen biomass-derived
pyrolysis oil effluent further inhibits secondary polymerization
reactions that otherwise result in increased viscosity and eventual
pressure differential elevation across the deoxygenating catalyst.
Therefore, a low-oxygen biomass-derived pyrolysis oil can be
produced in the hydroprocessing reactor without plugging the
deoxygenating catalyst, thereby increasing run duration and
improving processability of the biomass-derived pyrolysis oil.
[0060] While at least one exemplary embodiment has been presented
in the foregoing detailed description of the invention, it should
be appreciated that a vast number of variations exist. It should
also be appreciated that the exemplary embodiment or exemplary
embodiments are only examples, and are not intended to limit the
scope, applicability, or configuration of the invention in any way.
Rather, the foregoing detailed description will provide those
skilled in the art with a convenient road map for implementing an
exemplary embodiment of the invention. It being understood that
various changes may be made in the function and arrangement of
elements described in an exemplary embodiment without departing
from the scope of the invention as set forth in the appended
claims.
* * * * *