U.S. patent application number 12/969346 was filed with the patent office on 2012-06-21 for biofuel compositions and methods based on co-processing aromatic-rich and aromatic-lean components.
This patent application is currently assigned to UOP LLC. Invention is credited to ANDREA G. BOZZANO, CHRISTOPHER DAVID GOSLING, TOM N. KALNES.
Application Number | 20120152801 12/969346 |
Document ID | / |
Family ID | 46232978 |
Filed Date | 2012-06-21 |
United States Patent
Application |
20120152801 |
Kind Code |
A1 |
BOZZANO; ANDREA G. ; et
al. |
June 21, 2012 |
BIOFUEL COMPOSITIONS AND METHODS BASED ON CO-PROCESSING
AROMATIC-RICH AND AROMATIC-LEAN COMPONENTS
Abstract
Biofuel compositions obtained by the simultaneous
hydroprocessing of at least two distinct hydroprocessing
feedstocks, either or both of which are derived from biomass, are
disclosed. The co-processing of these feedstocks can result in an
upgraded product having suitable characteristics, in terms of
composition (e.g., quantities of compounds such as aromatic
hydrocarbons, present in relatively large amounts) and in terms of
quality (e.g., quantities of compounds such as oxygenates, present
in relatively small amounts) for use as a hydroprocessed biofuel
such as hydroprocessed aviation biofuel.
Inventors: |
BOZZANO; ANDREA G.;
(NORTHBROOK, IL) ; GOSLING; CHRISTOPHER DAVID;
(ROSELLE, IL) ; KALNES; TOM N.; (LAGRANGE,
IL) |
Assignee: |
UOP LLC
DES PLAINES
IL
|
Family ID: |
46232978 |
Appl. No.: |
12/969346 |
Filed: |
December 15, 2010 |
Current U.S.
Class: |
208/17 ; 208/108;
208/264; 208/56 |
Current CPC
Class: |
C10G 2300/1003 20130101;
C10J 2300/0916 20130101; C10G 2300/42 20130101; C10G 2300/1096
20130101; C10G 2/30 20130101; C10G 3/47 20130101; C10G 3/46
20130101; C10G 2300/1088 20130101; C10L 1/02 20130101; C10G
2300/1022 20130101; C10J 2300/1659 20130101; C10G 3/49 20130101;
Y02P 30/00 20151101; Y02P 30/20 20151101; C10G 3/52 20130101; C10J
2300/1618 20130101; Y02E 50/30 20130101; Y02E 50/32 20130101; Y02P
30/10 20151101; C10G 3/50 20130101; Y02T 50/678 20130101; C10G
2400/08 20130101; C10G 2300/1014 20130101; C10G 2300/807
20130101 |
Class at
Publication: |
208/17 ; 208/108;
208/264; 208/56 |
International
Class: |
C10L 1/04 20060101
C10L001/04; C10G 45/28 20060101 C10G045/28; C10G 47/00 20060101
C10G047/00 |
Claims
1. A method for making a fuel composition, the method comprising
contacting an aromatic-rich biomass derived component and an
aromatic-lean component with hydrogen under catalytic
hydroprocessing conditions to provide a hydroprocessed biofuel.
2. The method of claim 1, wherein the aromatic-lean component is
obtained from a combination of gasification and Fischer-Tropsch
synthesis.
3. The method of claim 2, wherein the aromatic-lean component
comprises olefinic hydrocarbons and oxygenated compounds.
4. The method of claim 1, wherein the aromatic-lean component is
derived from biomass and the aromatic-rich component is derived
from either biomass or tall oil.
5. The method of claim 4, wherein the aromatic-lean component is
derived from biomass independently selected from the group
consisting of hardwood, softwood, hardwood bark, softwood bark,
corn fiber, corn stover, sugar cane bagasse, switchgrass,
miscanthus, algae, waste paper, construction waste, demolition
waste, municipal waste, and mixtures thereof.
6. The method of claim 1, wherein the catalytic hydroprocessing
conditions result in both hydrotreating and hydrocracking
reactions.
7. The method of claim 1, wherein the aromatic-rich biomass derived
component is obtained from pyrolysis.
8. The method of claim 1, wherein the aromatic-rich biomass derived
component comprises tall oil rosin acids or eucalyptols.
9. The method of claim 8, wherein the aromatic-rich biomass derived
component is crude tall oil or depitched tall oil.
10. The method of claim 1, wherein the aromatic-rich biomass
derived component comprises from about 10% to about 50% of oxygen
by weight.
11. The method of claim 1, wherein the hydroprocessed biofuel is a
hydroprocessed aviation biofuel recovered from fractionation of a
hydroprocessed product of the contacting of the aromatic-rich
biomass derived component and the aromatic-lean component with
hydrogen.
12. The method of claim 11, wherein fractionation separates the
hydroprocessed aviation biofuel fraction from lower boiling
hydrocarbons and higher boiling hydrocarbons present in the
hydroprocessed product.
13. The method of claim 12, wherein the lower boiling hydrocarbons
comprise C.sub.4.sup.-1 hydrocarbons.
14. The method of claim 13, further comprising generating, from at
least a portion of the C.sub.4.sup.-1 hydrocarbons, at least a
portion of the hydrogen for contacting with the aromatic-rich
biomass derived component and the aromatic-lean component.
15. The method of claim 14, further comprising catalytically
reforming at least the portion of the C.sub.4.sup.-1 hydrocarbons
in the presence of steam to generate at least the portion of the
hydrogen for contacting with the aromatic-rich biomass derived
component and the aromatic-lean component.
16. The method of claim 11, further comprising blending the
hydroprocessed aviation biofuel fraction with from about 1% to 99%
by weight of a petroleum derived aviation fuel.
17. A fuel composition comprising a hydroprocessed aviation biofuel
obtained from hydroprocessing an aromatic-rich biomass derived
component and an aromatic-lean component.
18. The fuel composition of claim 17, wherein the hydroprocessed
aviation biofuel fraction comprises less than about 500 part per
million (ppm) of total organic oxygen by weight.
19. The fuel composition of claim 17, wherein the hydroprocessed
aviation biofuel fraction comprises at least about 99.5%
hydrocarbons by weight.
20. The fuel composition of claim 17, wherein the hydroprocessed
aviation biofuel fraction comprises at least about 3% aromatic
hydrocarbons by volume.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the hydroprocessing of both
aromatic-rich and aromatic-lean components, either or both of which
are derived from biomass, as well as hydroprocessed biofuels (e.g.,
aviation fuel) made from this co-processing. The present invention
also relates to such hydroprocessing methods, utilizing hydrogen
generated from biomass-derived C.sub.4.sup.- byproducts, in order
to further reduce the carbon footprint of the biofuel.
DESCRIPTION OF RELATED ART
[0002] Environmental concerns over fossil fuel greenhouse gas (GHG)
emissions have led to an increasing emphasis on renewable energy
sources. Wood and other forms of biomass including agricultural and
forestry residues are examples of some of the main types of
renewable feedstocks being considered for the production of liquid
fuels. Energy from biomass based on energy crops such as short
rotation forestry, for example, can contribute significantly
towards the objectives of the Kyoto Agreement in reducing GHG
emissions.
[0003] Gasification is a known process for the conversion of a wide
range of carbonaceous materials, such as coal and natural gas, into
a gaseous mixture containing carbon monoxide and hydrogen, referred
to as synthesis gas or syngas. The process involves contacting the
raw material in a gasification reactor with a controlled amount of
oxygen and/or steam to achieve partial oxidation but not complete
combustion. Representative processes for coal gasification to
syngas are described, for example, in WO 2006/070018; U.S. Pat. No.
4,836,146; and WO 2004/005438. In the case of biomass gasification,
in which the source of carbon is renewable, the incomplete
combustion generally results in a mixture called producer gas,
which includes small amounts of methane in addition to the CO and
H.sub.2. See, for example, Rajvanshi, A. K., "Biomass
Gasification," Ch. 4 of ALTERNATIVE ENERGY IN AGRICULTURE, Vol. II,
CRC Press, 1986, pp. 83-102. Other known routes for the production
of syngas from biomass include "hydro-gasification" (gasification
in the presence of hydrogen), to generate methane, followed by
steam reforming, pyrolytic reforming, or steam pyrolysis of the
methane. Representative processes are described, for example in
U.S. Pat. No. 7,619,012; US Publication 2005/0256212; and US
Publication 2005/0032920.
[0004] Once syngas is obtained, the Fischer-Tropsch (F-T) process
can be used for the further synthesis, from this feed, of
paraffinic hydrocarbons having from one carbon atom (methane) to
200 carbon atoms or even more. In particular, the syngas is fed to
an F-T reactor where it is converted over a suitable catalyst at
elevated temperature and pressure into these hydrocarbons. The F-T
process is described, for example, in WO 02/02489, WO 01/76736, WO
02/07882, EP 0 510 771 and EP 0 450 861. The combination of biomass
gasification and F-T synthesis therefore provides a Biomass to
Liquid (BTL) pathway for producing renewable fuel components.
[0005] In addition to BTL, pyrolysis is an alternative route for
obtaining liquid fuels, including transportation fuel and heating
oil, from biomass feedstocks. Pyrolysis refers to thermal
decomposition in the substantial absence of oxygen (or in the
presence of significantly less oxygen than required for complete
combustion). Initial attempts to obtain useful oils from biomass
pyrolysis yielded predominantly an equilibrium product slate (i.e.,
the products of "slow pyrolysis"). In addition to the desired
liquid product, roughly equal proportions of non-reactive solids
(char and ash) and non-condensable gases were obtained as unwanted
byproducts. More recently, however, significantly improved yields
of primary, non-equilibrium liquids and gases (including valuable
chemicals, chemical intermediates, petrochemicals, and fuels) have
been obtained from carbonaceous feedstocks through fast (rapid or
flash) pyrolysis, accompanied by a reduction in undesirable, slow
pyrolysis products.
[0006] The development of fuel compositions, and particularly those
useful as transportation fuels, which are derived at least partly
from renewable feedstocks such as biomass, is an ongoing objective
of major industrial importance. Of significant interest are
compositions, or fractions useful for blending into compositions,
having characteristics (e.g., energy content, distillation curve,
and density) that are representative of their counterpart petroleum
derived compositions or blending fractions, used for the same
intended purpose (e.g., as aviation fuel). Of further interest are
methods for producing such compositions and fractions in a manner
that exploits processing synergies and/or economies of scale,
thereby resulting in the lowest possible carbon footprint, based on
a lifecycle assessment of their GHG emissions.
SUMMARY OF THE INVENTION
[0007] The present invention is associated with the discovery of
fuel compositions exhibiting reduced greenhouse gas (GHG)
emissions, based on a lifecycle assessment (LCA) from the time of
cultivation of feedstocks (in the case of plant materials) required
for the compositions, up to and including the ultimate combustion
of the fuel composition by the end user. The compositions are
prepared by co-processing at least two distinct hydroprocessing
feedstocks, either or both of which are derived from biomass.
Advantageously, co-processing results in an upgraded,
hydroprocessed product (or an upgraded, hydroprocessed biofuel as a
hydroprocessed product fraction) having suitable characteristics,
in terms of composition (e.g., quantities of compounds such as
aromatic hydrocarbons, present in relatively large or minimally
required amounts) and in terms of quality (e.g., quantities of
thermally unstable compounds such as oxygenates, present in
relatively small amounts) for use as a fuel composition or
component thereof.
[0008] Aspects of the invention relate to the use hydroprocessing
to simultaneously upgrade (i) a hydroprocessing feedstock that is
rich in cyclic compounds, for example a crude or refined pyrolysis
oil or tall oil, together with (ii) a hydroprocessing feedstock
that is lean in aromatic compounds, for example the highly
paraffinic product obtained from gasification and Fischer-Tropsch
(F-T) synthesis. In component (i), namely the "aromatic-rich"
component, the cyclic compounds are effectively precursors to
aromatic compounds formed in the hydroprocessing. Both pyrolysis
oil and component (ii), namely the "aromatic-lean" component, such
as an F-T synthesis product, may be derived from biomass.
Particular embodiments of the invention are therefore directed to
hydroprocessing methods, or methods for making fuel compositions,
in which both the aromatic-rich component and the aromatic-lean
component are derived from biomass, or otherwise such methods in
which the aromatic lean component is derived from tall oil (e.g.,
tall oil rosin acids) and the aromatic-lean component is derived
from biomass.
[0009] Pyrolysis oil, either in its crude form (i.e., raw pyrolysis
oil) or treated to remove solid contaminants and soluble metallic
compounds, typically contains a high oxygen content and a low
energy content, relative to petroleum derived liquid fuel
fractions. Other properties of pyrolysis oil render it generally
unusable, in any appreciable proportion, as a component of a
transportation fuel composition. Likewise, the products of Biomass
to Liquid (BTL) pathways described above, which include the
products of gasification followed by F-T synthesis, are generally
of significantly lower quality, compared to their counterpart,
paraffin-rich petroleum derived products used for fuel blending.
This quality deficit results from the presence of oxygenates and
possibly olefins, with amounts of these non-paraffin impurities
depending on the F-T catalyst and processing conditions used.
Moreover, the high overall paraffin content characteristic of
products obtained from this reaction renders them unsuitable, even
in the absence of their oxygenate and olefin impurities, for use in
current commercial applications such as aviation fuel, unless
blended with aromatic hydrocarbons.
[0010] Hydroprocessing of both aromatic-rich and aromatic-lean
components advantageously provides simultaneous upgrading of at
least these two components, which, optionally followed by
fractionation of the resulting, hydroprocessed product, can provide
a hydroprocessed biofuel meeting applicable composition and quality
standards. In addition, the oxygenate content of the aromatic-rich
component, which is generally significantly higher than that of the
aromatic-lean component (e.g., derived from F-T synthesis), is
diluted during hydroprocessing. This further simplifies the overall
process, by reducing adiabatic temperature rise and the
corresponding production of undesirable coke precursors. According
to embodiments of the invention, a biofuel that does not require
further blending with aromatic hydrocarbons, such as an on-spec
aviation biofuel, is obtained after hydroprocessing and
fractionation.
[0011] Embodiments of the invention therefore relate to novel
production methods for fuel compositions that are at least
partially, but often completely, derived from renewable carbon
sources. These sources include an aromatic-rich biomass derived
component and an aromatic-lean component that may likewise be
biomass derived (e.g., from the BTL pathway, combining gasification
and F-T synthesis, as described above). Representative methods
comprise contacting these components with hydrogen together in a
common hydroprocessing reactor to achieve efficiencies and other
advantages, as discussed herein, compared to separately upgrading
these components. Following fractionation of the hydroprocessed
product, the resulting hydroprocessed biofuel (e.g., a
hydroprocessed aviation biofuel, having a significant quantity of
aromatic hydrocarbons) may be used in neat form (e.g., as an
aviation fuel) or otherwise blended, for example, with conventional
petroleum derived blending stocks. Whether or not the
hydroprocessed biofuel is blended, the carbon footprint of the
resulting neat biofuel or blended biofuel can be reduced.
[0012] Other embodiments of the invention relate to production
methods for hydroprocessed biofuel exhibiting a GHG emission, based
on a Life Cycle Assessment (LCA), which is further reduced by
virtue of using a biomass-derived source of hydrogen for the
hydroprocessing step. In particular, byproducts (e.g., light
hydrocarbons) of hydroprocessing, F-T synthesis, and/or pyrolysis
can be converted, according to an overall hydroprocessed biofuel
production process, in an integrated hydrogen generation unit. For
example, a catalytic steam reformer may be integrated with one or
more of a catalytic hydroprocessing unit, a F-T synthesis unit,
and/or a Rapid Thermal Processing (RTP) pyrolysis unit. Therefore,
at least a portion of the byproducts of any one or more of these
operations may be converted to hydrogen (e.g., by catalytic steam
reforming), thereby generating at least a portion of the hydrogen
required for hydroprocessing. Importantly, the generation of
hydrogen in this manner (i.e., from byproducts obtained from the
processing of feedstocks comprising renewable carbon) beneficially
reduces the amount of hydrogen that must be obtained from external
fossil sources (imported), thereby further lowering the lifecycle
GHG emission value of the resulting hydroprocessed biofuel.
According to other embodiments in which gasification and F-T
synthesis are used to provide the aromatic-lean component, a
portion of the syngas from gasification can be purified and used as
a renewable source of hydrogen for hydroprocessing.
[0013] Representative production methods include (i) the pyrolysis
of a first biomass feedstock to raw pyrolysis oil, to provide the
aromatic-rich component and also (ii) the gasification of a second
biomass feedstock, followed by F-T synthesis, to provide the
aromatic-lean component. Alternatively, the aromatic-rich component
may be obtained from other naturally occurring sources without
pyrolysis, such as from tall oil or oils derived from aromatic
foliage such as eucalyptols. The first and second biomass
feedstocks may comprise the same or different types of biomass,
and, according to particular embodiments, both components are
derived from second generation (e.g., lignocellulosic) biomass
feedstocks. The aromatic-rich and/or aromatic-lean components may
optionally be obtained after separation from (e.g., by
fractionation), and/or pretreatment of, the raw pyrolysis oil
and/or the F-T synthesis product, respectively, prior to
hydroprocessing. In any event, the subsequent hydroprocessing of
the aromatic-rich and aromatic-lean components beneficially reduces
their total oxygen content and increases their total heating
value.
[0014] The methods can further comprise separating an effluent or
product of hydroprocessing (e.g., a hydrotreating or hydrocracking
reactor effluent), for example, by fractionation and/or absorption,
to provide the hydroprocessed biofuel as a hydroprocessed product
fraction (e.g., a hydroprocessed aviation biofuel, a hydroprocessed
gasoline biofuel, etc.) comprising hydrocarbons having normal
boiling points characteristic of their counterpart petroleum
derived fractions used for the same application. It is also
possible to blend such petroleum derived fractions, in a subsequent
blending step, to provide the fuel compositions having a reduced
carbon footprint (i.e., exhibiting reduced GHG emissions based on
their LCA), by virtue of at least part of the carbon content of the
compositions being renewable.
[0015] Further embodiments of the invention relate to methods of
preparing fuel compositions. Representative methods comprise
blending a hydroprocessed product fraction, and particularly a
hydroprocessed biofuel made according to methods described herein,
with a petroleum derived component. Representative amounts of the
hydroprocessed product fraction (e.g., a hydroprocessed aviation
biofuel) and petroleum derived components are also described
herein.
[0016] These and other embodiments and aspects relating to the
present invention are apparent from the following Detailed
Description.
DETAILED DESCRIPTION
[0017] Representative methods for making a fuel composition,
according to embodiments of the invention, comprise contacting an
aromatic-rich biomass derived component and an aromatic-lean
component with hydrogen under catalytic hydroprocessing conditions
effective to deoxygenate and upgrade both of these components
simultaneously and provide a hydroprocessed biofuel meeting
industry specifications. The simultaneous co-processing results in
efficiencies and other advantages as described above. Preferably
both the aromatic-rich component and the aromatic-lean component
are derived from biomass to provide a hydroprocessed biofuel having
a carbon content that is all or substantially all derived from
renewable carbon. The carbon footprint of the biofuel is thereby
greatly reduced according to U.S. government greenhouse gas (GHG)
emission accounting practices, in which emissions associated with
the combustion of biomass derived fuels are not reported in the
lifecycle assessment (LCA) of the GHG emission value, since biomass
is renewed over a very short time frame compared to petroleum
derived components. Of particular interest with respect to the
biofuel compositions described herein are aviation (e.g., jet)
fuels.
[0018] Biomass suitable as a renewable carbon source for the
aromatic-rich component, for example a pyrolysis oil obtained using
Rapid Thermal Processing (RTP), can be any plant material, or
mixture of plant materials, including a hardwood (e.g., whitewood),
a softwood, or a hardwood or softwood bark. Energy crops, or
otherwise agricultural residues (e.g., logging residues) or other
types of plant wastes or plant-derived wastes, may also be used as
plant materials. Specific exemplary plant materials include corn
fiber, corn stover, and sugar cane bagasse, in addition to
"on-purpose" energy crops such as switchgrass, miscanthus, and
algae. Short rotation forestry products, as energy crops, include
alder, ash, southern beech, birch, eucalyptus, poplar, willow,
paper mulberry, Australian blackwood, sycamore, and varieties of
paulownia elongate. Other examples of suitable biomass include
organic waste materials, such as waste paper and construction,
demolition, and municipal wastes. In general, the pyrolysis derived
component (e.g., pyrolysis derived gasoline) may be obtained from
any feedstock comprising lignocellulosic biomass. Because the
biomass feedstocks are composed of the same building blocks, namely
cellulose, hemi-cellulose, and lignin, pyrolysis conditions are
relatively similar in the production of raw pyrolysis oils from
these various feedstocks.
[0019] These same types of biomass may also be independently
selected as a renewable carbon source for the aromatic-lean
component, for example obtained according to a Biomass to Liquid
(BTL) pathway involving Fischer-Tropsch (F-T) synthesis as
discussed above. Other types of biomass include waste plastic,
rubber, manure, and biosolids from waste water (sewage) treatment,
which may also be employed as feedstocks in the methods described
herein.
Aromatic-Rich Component
[0020] The "aromatic-rich" component is derived from biomass and
comprises a significant quantity, for example generally from about
5% to about 85%, and often from about 10% to about 75%, by weight
of cyclic compounds, including cyclic organic oxygenates. The term
"cyclic organic oxygenates" is meant to include compounds in which
oxygen is incorporated into a ring structure (e.g., a pyran ring),
as well as compounds (e.g., phenol) having a ring structure with
oxygen being incorporated outside the ring structure. In either
case, the ring structure may have from 3 to 8 ring members, be
fused to other ring structures, and may be completely saturated
(e.g., naphthenic), completely unsaturated (e.g., aromatic), or
partially unsaturated. After hydroprocessing, these cyclic
compounds, including cyclic organic oxygenates, can contribute to
the total aromatics content of the hydroprocessed biofuel. These
cyclic compounds are preferably obtained from natural sources, such
as lignocellulosic biomass, as described above, that has been
pyrolyzed to depolymerize and fragment the cyclic building blocks
of cellulose, hemicellulose, and lignin. According to
representative embodiments of the invention, the aromatic-rich
component is derived from biomass subjected to pyrolysis in an
oxygen depleted environment, for example using Rapid Thermal
Processing (RTP).
[0021] Fast pyrolysis refers generally to technologies involving
rapid heat transfer to the biomass feedstock, which is maintained
at a relatively high temperature for a very short time. The
temperature of the primary pyrolysis products is then rapidly
reduced before chemical equilibrium is achieved. The fast cooling
therefore prevents the valuable reaction intermediates, formed by
depolymerization and fragmentation of the biomass building blocks,
namely cellulose, hemicellulose, and lignin, from degrading to
non-reactive, low-value final products. A number of fast pyrolysis
processes are described in U.S. Pat. No. 5,961,786; Canadian Patent
Application 536,549; and by Bridgwater, A. V., "Biomass Fast
Pyrolysis," Review paper BIBLID: 0354-9836, 8 (2004), 2, 21-49.
Fast pyrolysis processes include Rapid Thermal Processing (RTP), in
which an inert or catalytic solid particulate is used to carry and
transfer heat to the feedstock. RTP has been commercialized and
operated with very favorable yields (55-80% by weight, depending on
the biomass feedstock) of raw pyrolysis oil. The pyrolysis oil, as
an aromatic-rich component, whether or not subjected to pretreating
prior to hydroprocessing as described above, is normally
characterized by a relatively high content of cyclic compounds,
which is generally from about 10% to about 90%, and typically from
about 20% to about 80%, by weight. These cyclic compounds are
precursors to aromatic hydrocarbons obtained through their further
reaction in the hydroprocessing step, which also beneficially
decreases the oxygenate content and increases the heating value of
the pyrolysis oil, as discussed in greater detail below.
[0022] According to other embodiments, cyclic compounds are
obtained from rosin acids of tall oil. Tall oil refers to a
resinous yellow-black oily liquid, which is namely an acidified
byproduct of the kraft or sulfate processing of pine wood. Tall
oil, prior to refining, is normally a mixture of rosin acids, fatty
acids, sterols, high-molecular weight alcohols, and other alkyl
chain materials. Distillation of crude tall oil may be used to
recover a tall oil fraction that is enriched in the rosin acids,
for use as an aromatic-rich component as described herein. The
aromatic-rich component may therefore comprise tall oil either in
its crude form or distilled (e.g., by vacuum distillation) to
remove pitch (i.e., depitched tall oil) or otherwise distilled to
concentrate the rosin acids, which are primarily abietic acid and
dehydroabietic acid but include other cyclic carboxylic acids. As
discussed above, the aromatic-rich component may in general be
obtained after separation from (e.g., by fractionation), and/or
pretreatment of, a raw pyrolysis oil or crude tall oil, prior to
hydroprocessing. In the former case, raw pyrolysis oil is often
subjected to pretreatment such as filtration to remove solids
and/or ion exchange to remove soluble metals, prior to
hydroprocessing.
[0023] Importantly, the aromatic-rich component can be
hydroprocessed to provide cyclic hydrocarbons, including aromatic
hydrocarbons in an amount governed by the equilibrium between
homologous naphthenic and aromatic ring structures under
hydroprocessing conditions of temperature and hydrogen partial
pressure, as described herein. According to preferred embodiments,
the aromatic-rich component is present in the combined
hydroprocessing feedstock (including both the aromatic-rich and
aromatic-lean components) in a quantity effective to obtain a
hydroprocessed biofuel or hydroprocessed biofuel fraction (e.g., a
hydroprocessed aviation biofuel) comprising aromatic hydrocarbons
generally in an amount of at least 2% by volume (e.g., from about
2% to about 25% by volume), typically in an amount of at least 3%
by volume (e.g., from about 3% to about 20% by volume), and often
in an amount of at least 8% by volume (e.g., from about 8% to about
15% by volume). Due to the nature of the cyclic compounds of the
aromatic-rich component, when derived from biomass, the aromatic
hydrocarbons in the resulting hydroprocessed product or
hydroprocessed biofuel fraction of this product (e.g.,
hydroprocessed aviation biofuel) generally include only minor
amounts of benzene and toluene. In representative embodiments, such
hydroprocessed biofuel fractions comprise generally less than about
3% by weight, and typically less than about 2% by weight, of
benzene and toluene combined.
Aromatic-Lean Component
[0024] The aromatic-lean component generally comprises non-cyclic,
and predominantly straight-chain paraffinic and olefinic
hydrocarbons, for example in an amount of generally from about 50%
to about 98%, and typically from about 75% to about 97%, by weight.
The amount of cyclic compounds in the aromatic-lean component is
generally less than about 3%, and often less than about 1%, by
weight. A representative aromatic-lean component is obtained from a
combination of gasification, for example of a biomass feedstock, to
provide syngas, followed by F-T synthesis to provide the mixture of
non-cyclic paraffinic and olefinic hydrocarbons, in proportions
governed substantially by the catalyst system used. In general, a
representative aromatic-lean component is the product of a BTL
pathway as discussed above. Like the aromatic-rich component, the
aromatic-lean component may also generally be obtained after
further processing steps, which in this case include separation
from (e.g., by fractionation), and/or pretreatment of, a BTL
product or other Fischer-Tropsch synthesis product, prior to
hydroprocessing. For example, the normally liquid phase product of
this synthesis may be separated from normally gas phase by-products
such as light hydrocarbons, as well as from other by-products, such
as water, according to known methods.
[0025] F-T synthesis of liquid fuel refers to a process for
converting syngas, namely a mixture of CO and H.sub.2, into
hydrocarbons of advancing molecular weight according to the
reaction:
n(CO+2H.sub.2).fwdarw.(--CH.sub.2--).sub.n+nH.sub.2O+heat.
[0026] Products of the F-T synthesis reaction may therefore range
from methane to heavy paraffin waxes. Normally, the production of
methane is minimized and a substantial portion of the hydrocarbons
produced have a carbon chain length of a least 5 carbon atoms.
Therefore, C.sub.5.sup.+ hydrocarbons are present in the F-T
reaction product in an amount generally of at least about 60%
(e.g., from about 60% to about 99%), and typically at least about
70% (e.g., from about 70% to about 95%) by weight. These amounts
are also representative of those in the aromatic-lean product, even
following conventional removal of light hydrocarbon (e.g., methane
and ethane) byproducts and water as described above.
[0027] F-T synthesis is carried out in the presence of an
appropriate catalyst and generally at elevated temperatures, for
example from about 125.degree. C. (257.degree. F.) to about
350.degree. C. (662.degree. F.), and typically from about
175.degree. C. (347.degree. F.) to about 275.degree. C.
(527.degree. F.). Suitable absolute pressures are generally from
about 0.5 MPa (75 psig) to 15 MPa (2200 psig), and typically from
about 0.7 MPa (100 psig) to about 3.5 MPa (500 psig). The F-T
synthesis may be carried out in a multi-tubular reactor, a slurry
phase regime or an ebullating bed regime, wherein the catalyst
particles are kept in suspension by an upward superficial gas
and/or liquid velocity.
[0028] Representative catalysts for the F-T synthesis of
hydrocarbons comprise, as the catalytically active component, a
metal from Group VIII of the periodic table, which is typically
selected from ruthenium, iron, cobalt, nickel and mixtures thereof.
The catalytically active metal or combination of metals is normally
disposed on a carrier, which may be a porous inorganic refractory
oxide, such as alumina, silica, titania, zirconia or mixtures
thereof. The amount of catalytically active metal may range
generally from about 1% to about 50% by weight, and typically from
about 2% to about 30% by weight. The catalytically active metal may
be present in the catalyst in combination with one or more metal
promoters or co-catalysts. These promoters may be metals or metal
oxides, for example the oxides of metals selected from Groups IIA,
IIIB, IVB, VB, VIIB and/or VIII of the Periodic Table, or oxides of
the lanthanides and/or the actinides. Particular representative F-T
catalysts comprise iron or cobalt as the catalytically active metal
and further comprise a promoter selected from the group consisting
of zirconium, manganese, and vanadium. Iron-containing F-T
catalysts are preferred for syngas feeds having a low H.sub.2
content, such as those derived from biomass, as this metal also
promotes the water-gas shift reaction to increase H.sub.2
availability. Other representative metal promoters include rhenium,
platinum, and palladium. Reference to groups of the Periodic Table
are based on the "previous IUPAC form" as described in the Handbook
of Chemistry and Physics (CPC Press), 68.sup.th Ed. As discussed
above, the particular catalyst system chosen, including the types
and amounts of metal(s) and promoters, as well as the type of
carrier, has a significant impact on the relative quantity of
olefins obtained in the F-T synthesis, relative to paraffins.
[0029] The syngas used for F-T synthesis may be obtained from a
wide variety of carbonaceous feedstocks through gasification (e.g.,
non-catalytic partial oxidation). Preferably, the syngas is
obtained from gasification of biomass, although other suitable
gasification feedstocks that do not necessarily include renewable
carbon may also be used. If the product of F-T synthesis is not
derived from any renewable carbon, then the renewable carbon of the
resulting hydroprocessed biofuel may be only that portion of the
total carbon that is obtained from the aromatic-rich component.
Carbonaceous feedstocks that are capable of being gasified to a
mixture of hydrogen and carbon monoxide include coal (e.g.,
anthracite, brown coal, bitumous coal, sub-bitumous coal, lignite,
and petroleum coke), bituminous oils, mineral crude oil or
fractions (e.g., resids) thereof, and methane containing feedstocks
(e.g., refinery gas, coal bed gas, associated gas, and natural
gas). Processes for converting such feedstocks to syngas are
described, for example, in "Gasification" by C. Higman and M van
der Burgt, Elsevier Science (USA), 2003, ISBN 0-7506-7707-4, Ch. 4
and 5. If desired, the H.sub.2:CO molar ratio obtained via
gasification may be adapted for the specific Fischer-Tropsch
catalyst and process. In case of syngas formed by gasification,
this molar ratio is generally less than about 1, for example in the
range from about 0.3 to about 0.9. It is possible to use such
H.sub.2:CO molar ratios in the Fischer-Tropsch synthesis, but more
satisfactory results may be obtained by increasing this ratio, for
example by performing a water-gas shift reaction or by adding
hydrogen to the syngas mixture. According to preferred embodiments,
the H.sub.2:CO ratio in the syngas is at least about 1.5, for
example in the range from about 1.6 to about 1.9.
Hydroprocessing
[0030] When the aromatic-lean component is a product of a BTL
pathway involving gasification of biomass and Fischer-Tropsch
synthesis as discussed above, this component is essentially free of
sulfur and aromatic hydrocarbons. However, this component also
generally contains oxygenates (e.g., aliphatic alcohols), such that
the total oxygen content of the aromatic-lean component is
typically in the range from about 0.25% to about 10%, and often
from about 0.5% to about 5%. Furthermore, reactive olefins may be
present in the aromatic-lean component in widely varying amounts,
depending on the particular F-T synthesis catalyst system, process,
and conditions used.
[0031] The raw pyrolysis oil obtained from a feedstock comprising
biomass, as described above, contains generally from about 20% to
about 50%, and often from about 30 to about 40%, by weight of total
oxygen, for example in the form of both (i) organic oxygenates,
such as hydroxyaldehydes, hydroxyketones, sugars, carboxylic acids,
and phenolic oligomers, and (ii) dissolved water. For this reason,
although a pourable and transportable liquid fuel, the raw
pyrolysis oil has only about 55-60% of the energy content of crude
oil-based fuel oils. Representative values of the energy content
are in the range from about 19.0 MJ/liter (69,800 BTU/gal) to about
25.0 MJ/liter (91,800 BTU/gal). Moreover, this raw product is often
corrosive and exhibits chemical instability due to the presence of
highly unsaturated compounds such as olefins (including diolefins)
and alkenylaromatics. Hydroprocessing of this pyrolysis oil is
therefore beneficial in terms of reducing its oxygen content and
increasing its stability, thereby rendering the hydroprocessed
product more suitable for blending in fuels, such as gasoline,
meeting all applicable specifications. As discussed above, the term
"pyrolysis oil," as it applies to a feedstock to the
hydroprocessing step, refers to the raw pyrolysis oil obtained
directly from pyrolysis (e.g., RTP) or otherwise refers to this raw
pyrolysis oil after having undergone pretreatment such as
filtration to remove solids and/or ion exchange to remove soluble
metals, prior to the hydroprocessing step.
[0032] As discussed above, the aromatic-lean component is
preferably obtained from BTL pathways.
[0033] These also include combined coal to liquid/biomass to liquid
(CTL/BTL) pathways, involving coal gasification, in which biomass
is added to the CTL unit to improve the carbon footprint of the
syngas used as a feed to F-T synthesis. For any BTL pathway
involving gasification of biomass followed by Fischer-Tropsch
synthesis, the aromatic-lean component contains predominantly
paraffinic or olefinic hydrocarbons, depending on the
Fischer-Tropsch catalyst system used. In either case, however,
oxygenates are present as impurities (e.g., as aliphatic alcohols)
in these hydrocarbons. Upgrading of the aromatic-lean component
through hydroprocessing, which normally involves hydrotreating to
remove oxygenates and other heteroatom-containing impurities, and
possibly hydrocracking to reduce average molecular weight, is
therefore beneficial for providing a desired fuel such as synthetic
paraffinic kerosene (SPK). This hydroprocessed biofuel, however,
cannot meet aviation fuel ASTM specifications (e.g., both density
and aromatic content) without the addition of aromatic
hydrocarbons.
[0034] Likewise, naturally derived oils rich in cyclic compounds
(and therefore useful as the aromatic-rich component in
compositions and methods of the present invention), including
pyrolysis oil, crude tall oil, and depitched tall oil, have a high
oxygenate content. In the case of tall oil, for example, rosin
acids (all multi-ring organic acids) are present in significant
concentrations. Deoxygenation of these oxygenated cyclic compounds
under hydroprocessing conditions beneficially yields aromatic
hydrocarbons. In combination with oxygen removal, ring saturation
and/or ring opening of at least one ring (but not all rings) of the
multi-ring compounds leads to the formation of napthenic and/or
alkylated cyclic hydrocarbons, respectively. Importantly, the
naphthenic/aromatic hydrocarbon equilibrium under the particular
hydroprocessing conditions used, may be used to govern the relative
proportions of these species and thereby meet desired
specifications for a particular application, for example the
content of aromatic hydrocarbons in the hydroprocessed aviation
biofuel.
[0035] Aspects of the invention are therefore associated with the
operational synergies that may be obtained by co-processing both
the aromatic-rich and aromatic-lean components to not only achieve
similar objectives (e.g., oxygenate removal) but also produce a
hydroprocessed biofuel that meets a number of important product
specifications, for example minimum aromatic content and maximum
total oxygen content in the case of jet fuel. According to some
embodiments, blending of the hydroprocessed biofuel with petroleum
derived aviation fuel and/or further processing, is not required to
achieve an "on-spec" fuel.
[0036] Hydroprocessing which includes hydrotreating (e.g.,
hydrodeoxygenation) and optionally hydrocracking reactions,
involves contacting the combined, aromatic-rich and aromatic-lean
components with hydrogen and in the presence of a suitable
hydroprocessing catalyst, generally under conditions sufficient to
convert a large proportion of the organic oxygenates in the
combined hydroprocessing feedstock to CO, CO.sub.2 and water that
are easily separated from the hydroprocessed product. The hydrogen
may be present in one or more streams, as discussed in greater
detail below. The hydrogen may be substantially pure (e.g., as
makeup or fresh hydrogen) or relatively impure (e.g., as recycle
hydrogen), as long as sufficient hydrogen partial pressure is
maintained in the reaction environment to achieve the desired
performance (e.g., conversion, catalyst stability, and product
aromatic content).
[0037] According to particular embodiments of the invention, the
aromatic-rich and aromatic-lean components may be mixed or combined
prior to the resulting mixture being contacted with any hydrogen.
In other embodiments, one component may be contacted with hydrogen
upstream of contacting with the other component (which may
similarly have been contacted with a separate hydrogen stream).
Optionally, streams containing the aromatic-rich and aromatic-lean
components (either or both of which having been previously
contacted with hydrogen) may be combined and optionally contacted
with hydrogen, for example as a separate hydrogen stream. According
to yet further embodiments, streams containing portions of the
aromatic-rich and/or aromatic-lean components (any of which, any
combination of which, or all of which having been previously
contacted with hydrogen) may be combined and the combined streams
optionally contacted further with hydrogen. The important
consideration is that, at some point in the hydroprocessing, the
aromatic-rich and aromatic-lean components are in the presence of
the same hydroprocessing catalyst and conditions, thereby gaining
efficiencies and other advantages associated with co-processing, as
described above.
[0038] Typical hydroprocessing conditions, under which the
aromatic-rich and aromatic-lean components are co-processed,
include an average catalyst bed temperature from about 40.degree.
C. (104.degree. F.) to about 538.degree. C. (1000.degree. F.),
often from about 150.degree. C. (302.degree. F.) to about
426.degree. C. (800.degree. F.), and a hydrogen partial pressure
from about 3.5 MPa (500 psig) to about 21 MPa (3000 psig), often
from about 6.2 MPa (800 psig) to about 10.5 MPa (1500 psig). In
addition to pressure and temperature, the residence times of the
aromatic-rich and aromatic-lean components in the presence of
hydroprocessing catalyst (e.g., disposed in one or more catalyst
beds or zones) can also be adjusted to increase or decrease the
reaction severity and consequently the quality of the resulting
hydroprocessed biofuel. With all other variables unchanged, lower
residence times are associated with lower reaction severity. The
inverse of the residence time is closely related to a variable
known as the Liquid Hourly Space Velocity (LHSV, expressed in units
of hr.sup.-1), which is the volumetric liquid flow rate over the
catalyst bed divided by the bed volume and represents the
equivalent number of catalyst bed volumes of liquid processed per
hour. Therefore, increasing the LHSV or hydroprocessing feedstock
flow rate, processed over a given quantity of catalyst,
directionally decreases residence time and the conversion of
undesirable compounds present in this oil, such as organic
oxygenate compounds. A typical range of LHSV for mild hydrotreating
according to the present invention is from about 0.1 hr.sup.-1 to
about 10 hr.sup.-1, often from about 0.5 hr to about 3 hr .sup.-1.
The quantity of hydrogen used may be based on the stoichiometric
amount needed to convert organic oxygenates to hydrocarbons and
H.sub.2O. In representative embodiments, hydroprocessing is carried
out in the presence of hydrogen in amount ranging from about 90% to
about 600% of this stoichiometric amount.
[0039] The hydroprocessing catalyst may be present in the form of a
fixed bed of particles comprising a catalytically active metal
disposed on a support, with suitable metals and supports being
described below. Otherwise the catalyst, either supported or
otherwise unsupported (e.g., in the form of fine particles of a
compound containing the catalytically active metal), may be used in
a back-mixed bed, such as in the case of a slurry reactor.
Homogeneous systems operating with catalysts that are soluble in
the reactants and products may also be used. Catalytic
hydroprocessing conditions will vary depending on the quality of
the hydroprocessed biofuel desired, with higher severity operations
directionally resulting in greater conversion of organic oxygenates
and other undesirable compounds (e.g., reactive olefins and
diolefins) by hydrogenation.
[0040] Suitable hydroprocessing catalysts include those comprising
of at least one Group VIII metal, such as iron, cobalt, and nickel
(e.g., cobalt and/or nickel) and at least one Group VI metal, such
as molybdenum and tungsten, on a high surface area support material
such as a refractory inorganic oxide (e.g., silica, alumina,
titania, and/or zirconia). A carbon support may also be used. A
representative hydroprocessing catalyst therefore comprises a metal
selected from the group consisting of nickel, cobalt, tungsten,
molybdenum, and mixtures thereof (e.g., a mixture of cobalt and
molybdenum), deposited on any of these support materials, or
combinations of support materials. The choice of support material
may be influenced, in some cases, by the need for corrosion
resistance in view of the presence of aqueous acids, for example in
the aromatic-rich component (e.g., pyrolysis oil) as a feedstock to
hydroprocessing.
[0041] The Group VIII metal is typically present in the
hydroprocessing catalyst in an amount ranging from about 2 to about
20 weight percent, and normally from about 4 to about 12 weight
percent, based on the volatile-free catalyst weight. The Group VI
metal is typically present in an amount ranging from about 1 to
about 25 weight percent, and normally from about 2 to about 25
weight percent, also based on the volatile-free catalyst weight. A
volatile-free catalyst sample may be obtained by subjecting the
catalyst to drying at 200-350.degree. C. (392-662.degree. F.) under
an inert gas purge or vacuum for a period of time (e.g., 2 hours),
so that water and other volatile components are driven from the
catalyst.
[0042] Other suitable hydroprocessing catalysts include zeolitic
catalysts, as well as noble metal catalysts where the noble metal
is selected from palladium and platinum. It is within the scope of
the invention to use more than one type of hydroprocessing catalyst
in the same or a different reaction vessel. Two or more
hydroprocessing catalyst beds of the same or different catalyst and
one or more quench points may also be utilized in a reaction vessel
or vessels to provide the hydroprocessed biofuel.
[0043] After hydroprocessing, the resulting hydroprocessed biofuel
has an oxygen content that is generally reduced from about 90% to
about 100% (i.e., complete or substantially complete oxygen
removal), relative to the oxygen present in the feedstock to
hydroprocessing, for example the oxygen present in the combined
aromatic-rich and aromatic-lean components, optionally after any
pretreatment prior to hydroprocessing. Importantly, the heating
value, on a mass basis, of the hydroprocessed biofuel is
simultaneously increased, typically by a factor ranging from about
1.5 to about 3, compared to that of the feedstock to
hydroprocessing. Fractionation or other separation methods may be
used to separate various fractions of the hydroprocessed product
(or total hydroprocessing effluent), which includes the
hydroprocessed biofuel such as a hydroprocessed aviation biofuel.
These fractions or hydroprocessed biofuels, in addition to having
been fractionated may also be obtained after other treatments
including catalytic reaction (e.g., for further oxygen removal)
and/or adsorption. The separated, hydroprocessed biofuel fraction
may then, according to some embodiments, be blended with comparable
petroleum derived fractions and possibly other suitable
additives.
[0044] In addition to a hydroprocessed aviation or jet fuel, other
fractions that may be recovered from separation (e.g.,
fractionation) of the hydroprocessed product include a
hydroprocessed gasoline biofuel, a hydroprocessed kerosene biofuel,
and/or a hydroprocessed diesel biofuel, as fractions having
successively higher boiling point ranges. Likewise, lower boiling
point range components may also be recovered by fractionation.
These include, for example, a hydroprocessed renewable analogue of
liquefied petroleum gas (LPG). After hydroprocessing and
fractionation, the hydroprocessed biofuel fractions described
above, including hydroprocessed aviation biofuel, comprise
predominantly hydrocarbons, typically at least about 90%
hydrocarbons (e.g., from about 90% to about 99.9% hydrocarbons) by
weight, and often at least about 97% hydrocarbons (e.g., from about
97% to about 99.5% hydrocarbons) by weight.
[0045] A hydroprocessed aviation biofuel may therefore be separated
from the hydrocarbon-containing products of hydroprocessing, based
on boiling point or relative volatility, in a distillation column
capable of carrying out a suitable number of theoretical stages of
equilibrium contacting between rising vapor and falling liquid.
According to representative embodiments, the hydroprocessed
aviation biofuel will have an initial boiling point temperature
characteristic of C.sub.5 hydrocarbons, for example from about
30.degree. C. (86.degree. F.) to about 40.degree. C. (104.degree.
F.) and a distillation end point temperature generally from about
138.degree. C. (280.degree. F.) to about 300.degree. C.
(572.degree. F.), and typically from about 145.degree. C.
(293.degree. F.) to about 288.degree. C. (550.degree. F.). These
boiling point temperatures, which are also characteristic of
petroleum derived aviation fuel fractions, are measured according
to ASTM D86.
[0046] A hydroprocessed aviation biofuel component or other
hydroprocessed biofuel fraction, therefore, may be separated by
fractionation from lower boiling hydrocarbons contained in a more
volatile component (e.g., a hydroprocessed analogue of LPG) and/or
higher boiling hydrocarbons contained in a less volatile component
(e.g., a hydroprocessed kerosene biofuel and/or a hydroprocessed
diesel biofuel). According to preferred embodiments, the separated,
lower boiling hydrocarbons comprise C.sub.4 hydrocarbons (e.g.,
butanes and butenes) as well as lower boiling compounds, such that
these lower boiling hydrocarbons may be referred to a C.sub.4.sup.-
hydrocarbons. To further reduce the GHG emission value, based on
LCA, of the hydroprocessed aviation biofuel or other hydroprocessed
biofuel fraction(s), at least a portion of these biomass-derived
C.sub.4.sup.- hydrocarbons are advantageously used to generate at
least a portion of the hydrogen required for contacting with the
aromatic-rich and/or aromatic-lean components during the
hydroprocessing.
[0047] The conversion of the lower boiling hydrocarbons, contained
in a less valuable, hydroprocessed biofuel fraction, to hydrogen,
can reduce or even eliminate the need for an external source of
hydrogen. This external hydrogen, if derived from fossil fuel,
would otherwise add to the carbon footprint associated with the
production of the hydroprocessed biofuel described herein, thereby
increasing the GHG emissions based on LCA. Integrated hydrogen
production is therefore beneficial in minimizing the GHG emissions
exhibited by any of the hydroprocessed biofuel fraction(s)
associated with the present invention. According to particular
embodiments, the C.sub.4.sup.-1 hydrocarbons are catalytically
reformed in the presence of steam. Representative steam reforming
catalysts include alumina supported nickel oxide.
[0048] Whether or not integrated hydrogen production is used, the
oxygen content remaining in the hydroprocessed aviation biofuel or
other hydroprocessed biofuel fraction(s) described above is a
function of the severity of the hydroprocessing operation, with
higher severity resulting in a higher conversion of organic
oxygenates to CO, CO.sub.2, and water, which may be easily removed.
While a reduction in organic oxygenates directionally increases
heating value, this improvement in the quality of a hydroprocessed
biofuel fraction is achieved at the expense of increased energy
required for the hydroprocessing operation. Optimization of the
organic oxygen content is therefore possible, depending on the
particular biomass used as feedstock, the particular fuel (or fuel
blend) composition, and its intended end use (e.g., for land
transport, in the case of gasoline or diesel fuels that allow more
than trace quantities of oxygenates).
[0049] Representative hydroprocessed biofuel fractions, other than
hydroprocessed aviation biofuel, generally contain from about
0.001% to about 5%, typically from about 0.02% to about 4%, and
often from about 0.05% to about 3%, by weight of organic oxygenates
that are relatively refractory under hydroprocessing conditions.
These ranges also apply to cyclic organic oxygenates (e.g., phenol
and alkylated phenols), which normally account for most or
substantially all of the organic oxygenates of a given
hydroprocessed biofuel fraction(s). In view of these amounts of
cyclic organic oxygenates a given hydroprocessed biofuel fraction,
representative fuel compositions (e.g., containing one or more
petroleum derived fractions) that are blended with such a
hydroprocessed biofuel fraction will generally contain from about
0.0005% to about 2.5%, typically from about 0.01% to about 2%, and
often from about 0.025% to about 1.5%, by weight of cyclic organic
oxygenates. According to other embodiments, these ranges may be
representative of the total phenol content, including alkylated
phenols, in the fuel composition. In the case of hydroprocessed
aviation biofuel, the total organic oxygen content remaining after
hydroprocessing, fractionation, and optionally additional
treatments as described above, is generally less than 0.5% by
weight to meet ASTM thermal stability test specifications for
aviation fuel. Preferably, the total organic oxygen content of the
aviation biofuel is less than about 500 parts per million (ppm) by
weight and more preferably less than about 300 ppm by weight. The
hydrocarbon content of such aviation biofuels is therefore
generally at least about 99.5% by weight, and the aromatic
hydrocarbon content is as discussed above.
[0050] The hydroprocessed aviation biofuel or other hydroprocessed
biofuel fraction(s) as described above, also advantageously share a
number of important characteristics with their petroleum derived
counterpart components. In terms of energy content, these fractions
may have a lower heating value generally from about 42 MJ/kg
(18,100 BTU/lb) to about 46 MJ/kg (19,800 BTU/lb) and typically
from about 43 MJ/kg (18,500 BTU/lb) to about 45 MJ/kg (19,400
BTU/lb). While these hydroprocessed biofuel fractions can meet
various standards required of their petroleum derived counterparts,
their carbon footprint is greatly reduced according to U.S.
government GHG emission accounting practices, in which emissions
associated with the combustion of biomass derived fuels are not
reported in the GHG emission value based on LCA, as discussed
above. According to particular embodiments of the invention, in
which the hydroprocessed biofuel or other hydroprocessed biofuel
fraction(s) is derived completely from biomass and/or other
renewable carbon sources, the lifecycle greenhouse gas emission
value of such biofuel fraction(s), based on CO.sub.2 equivalents,
is/are generally from about 5 g CO.sub.2-eq./MJ (11.6 lb CO.sub.2
eq/mmBTU) to about 50 g CO.sub.2-eq./MJ (116.3 lb
CO.sub.2-eq./mmBTU), typically from about 15 g CO.sub.2-eq./MJ
(34.9 lb CO.sub.2 eq./mmBTU) to about 35 g CO.sub.2-eq./MJ (81.3 lb
CO.sub.2-eq/mmBTU), and often from about 20 g CO.sub.2-eq./MJ (46.5
lb CO.sub.2-eq./mmBTU) to about 30 g CO.sub.2-eq./MJ (69.8 lb
CO.sub.2-eq/mmBTU), as measured according to guidelines set forth
by the Intergovernmental Panel on Climate Change (IPCC) and the
U.S. federal government. LCA values of emissions in terms of
CO.sub.2 equivalents, from raw material cultivation (in the case of
plant materials) or raw material extraction (in the case of fossil
fuels) through fuel combustion, can be calculated using SimaPro 7.1
software and IPCC GWP 100a methodologies.
[0051] According to representative fuel compositions associated
with the present invention, the hydroprocessed aviation biofuel or
other hydroprocessed biofuel fraction as described above may be
blended with a petroleum derived aviation fuel or other petroleum
derived fraction that is present in the resulting fuel composition
in an amount from about 30% to about 98% by weight. According to
particular fuel compositions, (i) generally from 1 to about 99%,
and typically from 1 to about 30%, of the hydroprocessed biofuel
fraction by weight is blended with (ii) generally from about 1% to
about 99%, and typically from about 70% to about 99% of a petroleum
derived fraction by weight.
[0052] Overall, aspects of the invention are directed to methods of
making fuel compositions comprising contacting, with hydrogen, a
feedstock to a hydroprocessing step. The feedstock comprises both
aromatic-rich and aromatic-lean components, either or both of which
may be derived from biomass. According to some embodiments, for
example, the aromatic-rich component may be derived from fossil
fuels and the aromatic-lean component may be derived from biomass.
Those having skill in the art, with the knowledge gained from the
present disclosure, will recognize that various changes could be
made in these methods, as well as compositions made by these
methods, without departing from the scope of the present invention.
Mechanisms used to explain theoretical or observed phenomena or
results, shall be interpreted as illustrative only and not limiting
in any way the scope of the appended claims.
* * * * *