Catalytic valorization of the acetate fraction of biomass to aromatics and its integration into the carboxylate platform

Article abstract of DOI:10.1039/c9gc00513g

In many plant species, the acetate fraction is the fourth most prominent fraction by weight after cellulose, hemicellulose and lignin, and can be easily extracted as a single stable molecule, acetic acid, at high yields. Despite this, upgrading the acetate fraction of biomass has received very limited attention. Here, we demonstrate a valorization route for the acetate fraction as well as mixtures of acetic acid and other volatile fatty acids produced from the polysaccharide fraction. Aqueous solutions of acetic acid, including solutions produced during steam explosion pretreatment and subsequently purified can be upgraded at high selectivity to a valuable mixture of aromatics, substituted cycloalkenes and gas olefins in a single step using Cu/ZrO₂. The catalyst displays remarkable stability despite the presence of acids, water and other biomass-derived impurities. We also show that acetic acid can be further valorized over the same catalyst by converting it in the presence of butanoic acid that was produced in a consolidated bioprocess from the same pretreated wood that was the source of the acetic acid. In this case, the acetic acid rapidly ketonizes with the butanoic acid and the resulting beta-ketones further condense to form aromatics and cycloalkenes with a higher average carbon number than those produced solely from acetic acid. Overall, our process yields a biomass-derived organic oil consisting of aromatics and cycloalkenes that spontaneously separates from water, can be tuned by varying the incoming mixture of carboxylic acids and has suitable properties for being used as a direct blend with aviation fuel.

Full text of DOI:10.1039/c9gc00513g

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J. H. Yeap, A. Elkhaiary, M. Talebi Amiri, R. L. Shahab, Y. Questell-Santiago, C. Xiros, B. P. Le Monnier, M.
H. Studer and J. Luterbacher, Green Chem., 2019, DOI: 10.1039/C9GC00513G.
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Heterogeneous catalytic oxidation for lignin valorization into valuable
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DOI: 10.1039/C9GC00513G
Journal Name
ARTICLE
Catalytic valorization of the acetate fraction of biomass to
aromatics and its integration into the carboxylate platform†
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
a
a
Bartosz Rozmysłowicz,‡ Jher Hau Yeap,‡ Ahmed M. I. Elkhaiary, Masoud Talebi Amiri, Robert L.
ab
a
b
a
Shahab, Ydna M. Questell-Santiago, Charilaos Xiros, Benjamin P. Le Monnier, Michael H.
DOI: 10.1039/x0xx00000x
b
a
Studer and Jeremy S. Luterbacher*
www.rsc.org/
In many plant species, the acetate fraction is the fourth most prominent fraction by weight after cellulose, hemicellulose
and lignin, and can be easily extracted as a single stable molecule, acetic acid, at high yields. Despite this, upgrading the
acetate fraction of biomass has received very limited attention. Here, we demonstrate a valorization route for the acetate
fraction as well as mixtures of acetic acid and other volatile fatty acids produced from the polysaccharide fraction.
Aqueous solutions of acetic acid, including solutions produced during steam explosion pretreatment and subsequently
purified can be upgraded at high selectivity to a valuable mixture of aromatics, substituted cycloalkenes and gas olefins in
2
a single step using Cu/ZrO . The catalyst displays remarkable stability despite the presence of acids, water and other
biomass-derived impurities. We also show that acetic acid can be further valorized over the same catalyst by converting it
in the presence of butanoic acid that was produced in a consolidated bioprocess from the same pretreated wood that was
the source of the acetic acid. In this case, the acetic acid rapidly ketonizes with the butanoic acid and the resulting beta-
ketones further condense to form aromatics and cycloalkenes with a higher average carbon number than those produced
solely from acetic acid. Overall, our process yields a biomass-derived organic oil consisting of aromatics and cycloalkenes
that spontaneously separates from water, can be tuned by varying the incoming mixture of carboxylic acids and has
suitable
properties
for
being
used
as
a
direct
blend
with
aviation
fuel.
Broader context
Lignocellulosic biomass represents one of two major sources of renewable carbon on the planet along with atmospheric carbon dioxide. As such, it represents an especially
attractive source of carbon for producing molecules that are still difficult to produce from CO and for applications that are difficult to meet with alternate forms of renewable
2
energy like electricity. Bio-based jet fuel production meets both of these criteria and for this reason, has garnered significant research attention. However, within this context very
little attention has been paid to the acetate fraction of biomass, which, though it is significantly smaller than the three major biopolymers in lignocellulosic biomass, can be easily
recovered at high yields early in biomass processing. Furthermore, other carboxylic acids can be produced from the remaining biomass fractions through the carboxylate platform.
Altogether, biomass-derived carboxylic acids offer opportunities for chemical upgrading because they feature a single functional group. Here, we show that this functionality can
be targeted in a single heterogeneously catalyzed process to achieve the required deoxygenation and chain lengthening reactions to produce a workable Jet A-1 fuel blend.
chemicals. Plants that are classified as lignocellulosic biomass
Introduction
Lignocellulosic biomass is the most abundant terrestrial source
of fixed renewable carbon and, because of this, is receiving
increasing attention as a source of sustainable fuels and
contain ~50-65% polysaccharides and ~10-30% lignin. The
polysaccharide fraction is generally composed of about two-
thirds six-carbon sugars (mostly glucose) and one-third five-
carbon sugars (mostly xylose). Lignin is a complex polymer
composed of phenyl propanoid units. Because of the
prominence of the polysaccharide and lignin polymers in
biomass, upgrading efforts have largely focused on sugars and
a. Laboratory of Sustainable and Catalytic Processing, Institute of Chemical Sciences
and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015
Lausanne, Switzerland. Email: jeremy.luterbacher@epfl.ch
1
phenolic monomers. However, carboxylic acids are also a very
attractive target.
b.
Laboratory of Biofuels and Biochemicals, School of Agricultural, Forest and Food
Sciences, Bern University of Applied Sciences (BFH), CH-3052 Zollikofen,
Switzerland.
†Electronic Supplementary Information (ESI) available: Chemicals and materials,
experimental procedure for catalyst preparation, catalyst characterization,
catalytic testing, lower heating value (LHV) estimation, ICP-MS analysis, aviation
fuel testing, electron microscopy imaging, production of acetic and butanoic acid
from beech wood and purification of acetic and butanoic acid. Supplementary
figures S1 – S12. Supplementary table S1. See DOI: 10.1039/x0xx00000x
‡
Co-first authors who contributed equally to this work.
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Journal Name
Fig. 1 Model structures for the three principle lignocellulosic biomass polymers.
Bell and co-workers demonstrated that reactions similar to
acetone condensation could occur with a variety of methyl
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DOI: 10.1039/C9GC00513G
ketones (or beta-ketones) over a base catalyst leading to
mixtures of substituted cycloalkanes and aromatic
1
7
molecules. In their work, the proposed source of beta-
ketones is either a hybrid biological and chemical pathway
where a mixture of biologically produced acetone, butanol and
ethanol (ABE) undergoes acetone alkylation, or deoxygenation
and ring opening of carbohydrate-derived furans. In both
cases, the associated chemical transformations involve several
steps, which limits yields and selectivity to single products.
In this work, we explored the upgrading of an aqueous
solution of acetic acid that was easily produced during biomass
pretreatment through combined ketonization and cascade
aldol condensation reactions. The objective of combining these
two pathways was to produce deoxygenated molecules with a
longer carbon chain in a single step for use as a fuel, which has
been a significant challenge especially in the presence of
The acetate fraction (~1-5 wt% of biomass) is highlighted in red.
Significant amounts of acetate groups are attached to the
hemicellulose fraction of biomass bound to xylopyranosyl
residues (Fig. 1). Mansfield and co-workers reported that
2
acetate groups represent between 6.7 and 3.5 wt% of poplar.
These acetate groups are much easier to remove from biomass
than lignin or polysaccharide monomers. Using relatively mild
dilute acid, basic or even neutral conditions, the acetate
groups are easily cleaved to produce a single product: acetic
acid. This cleavage happens at conditions where only some of
the hemicellulose is extracted. Furthermore, unlike lignin
8
water. The jet fuel range (hydrocarbon length from C to C16) is
monomers3 or sugars, acetic acid is stable and does not
degrade/re-polymerize making it relatively easy to extract at
high yields. Despite the relatively small levels of carboxylic
acids in biomass, it represents large amounts of product at the
biorefinery scale. Furthermore, acetic acid is often a significant
by-product in the carboxylate platform, which consists of
converting biomass-derived sugars to a mixture of carboxylic
acids. A prominent example of this route is the MixAlco
process developed by Holtzapple and co-workers and where
,4
5,6
a particularly attractive target because it represents a fuel that
requires a source of renewable carbon as it cannot be
substituted with renewable electricity.
In addition to acetic acid, we also tested an alternate
valorization path for acetic acid in the presence of longer chain
carboxylic acids, which is a typical mixture associated with the
carboxylate platform. We targeted the cross-ketonization of
acetic acid with longer chain carboxylic acids (in this case
butyric acid produced directly from pretreated biomass) to
form beta-ketones, which could condense similarly to acetone.
4
0-60% of the mixture of carboxylic acids that is produced
7
–9
from biomass is composed of acetic acid.
Despite the
prominence of acetic acid in biomass and various biomass
conversion routes, its valorization as a primary biomass- Results and Discussion
derived platform molecule has received limited attention.
Furthermore, the valorization of the acetate fraction of
biomass has received almost no attention. Instead, most
studies have focused on acetic acid conversion in the context
of pyrolysis oil upgrading, where it serves as an attractive
1
0–12
model compound for a carboxylic acid group.
Within this
context, a route that is often explored, including in the
MixAlco process, is the ketonization of acetic acid to acetone,
which allows for the significant removal of oxygen as CO
2
without the need for external hydrogen. Ketonization is
typically catalyzed by salts or metal oxides at high
9
,10,13
temperatures (>300 °C).
Biomass-derived acetone is an
attractive substitute for its fossil-derived counterpart but can
also be further upgraded. Román-Leshkov and co-workers
1
4
showed that it could be catalytically upgraded to propylene
or isobutene12 over MoO
and zinc-zirconia, respectively.
3
Acetone can also be successively self-condensed over acid and
base catalysts first to mesityl oxide and then to mixtures of
cyclohexanes and aromatics (e.g. mesitylene, isophorone, etc.)
1
5,16
by further condensation and ring closing reactions.
However, all of these reactions are difficult to perform when
starting with aqueous mixtures of acetic acid because the acid
and water tend to deactivate catalytic sites that promote
1
4
ketone deoxygenation or condensation.
2
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Below, we discuss the potential reaction pathways that
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occurred on this catalyst for solutions of both pure acetic acid
or mixtures of butanoic and acetic acid.
Reaction pathway of pure acetic acid over Cu/ZrO . Two
2
acetic acid molecules could ketonize to form acetone (Fig. 2A),
losing one molecule of carbon dioxide in the process and
reducing the O/C ratio from 1 to 0.33. As the primary
intermediate, acetone could react further in two different
pathways. Hydrogenation of acetone produced isopropanol,
which dehydrated over the metal oxide to form propylene. An
alternate pathway was the subsequent aldol condensation of
two acetone molecules to form mesityl oxide. This step
lengthened the carbon chain length to six carbons. Further
cascade aldol condensations produced products with higher
9
carbon numbers (C to C15). Once the carbon backbone
exceeded six carbons, intramolecular condensations/ring-
closing reactions began to play a significant role forming
aromatics and cycloalkenes. For instance, phorone or 4,6-
9
dimethylhepta-3,5-dien-2-one (C ) could undergo ring-closing
to form isophorone and intramolecular condensation to form
mesitylene, respectively. Importantly, although Cu is a mild
hydrogenation catalyst, some hydrogenation could still occur
at all steps. A small proportion of acetic acid could be
hydrogenated before ketonization and subsequently add to
the aldol condensation products, forming a number of
compounds with carbon numbers that were not a multiple of
three, which could also be formed by decomposition or
Proposed reaction pathway
Fig. 2 Proposed and simplified reaction pathway for the ketonization of
carboxylic acids and subsequent cascade aldol condensation reactions to form
aromatic hydrocarbons with high carbon numbers. A) Starting with pure acetic
acid and performing direct ketonization. Catalytic sites are highlighted in blue
methane release of higher carbon number compounds (C
9
to
C
8
such as isophorone to 3,5-xylenol and methane). Cracking
and yellow. The main pathway is highlighted in red. B) Starting with a mixture of reactions could also occur, such as mesityl oxide forming acetic
acetic and butanoic acid and performing primarily cross-ketonization. The
catalytic sites are not highlighted for simplicity.
acid and isobutylene. As will be discussed below, through this
reaction pathway, the products separated into a triphasic
mixture of (i) organic oil formed by a mixture of largely
deoxygenated molecules with carbon numbers C to C15, (ii) an
8
In the process of upgrading short-chain carboxylic acids to
potential liquid aviation fuel additives, the carbon chain length
must be increased and a significant amount of oxygen
removed. Ideally, chain elongation and deoxygenation should
occur in a single step. Direct hydrogenation of the carboxylic
acids would only result in short gas hydrocarbons. Therefore,
we explored conditions that lead to the initial ketonization of
the carboxylic acids, and that were conducive to subsequent
aldol condensation reactions.
aqueous phase with water formed by deoxygenation reactions
or any water in the feed, and unreacted oxygenates (molecules
with at least one oxygen atom), and (iii) gas products
consisting of CO
2
and short chain hydrocarbons.
Reaction pathway of acetic & butanoic acid over Cu/ZrO
2
.
Rather than ketonizing acetic acid with itself, upgrading a
mixture of acetic acid and butanoic acid introduced possible
cross-ketonization reactions into the reaction pathway (Fig.
We chose Cu supported on ZrO
carboxylic acid upgrading. As mentioned above, ZrO
previously reported to catalyze the ketonization of carboxylic
2
as the catalyst for
2
B). Given that mixtures of acetic and longer chain carboxylic
2
was
acids are commonly produced during the carboxylate platform,
such a mixture and reaction scheme could be leveraged to
increase the average carbon number of the resulting organic
oil. Cross-ketonization proceeded in a similar fashion to direct
ketonization, forming β-ketones that could then undergo
cascade aldol condensation reactions. Acetone, 2-pentanone
and 4-heptanone were potential intermediates, any
combination of which could undergo aldol condensation.
Similarly, this mechanism also led to a three phase mixture of
products, with an organic oil phase containing aromatics and
cycloalkenes of higher average carbon number due to the
longer chain starting reactants compared to only acetic acid.
1
0
acids. Separately, it has also been used to perform aldol
condensation.12 The combination of these two reactions could
deoxygenate the substrate while increasing the carbon chain
length in one step. The addition of Cu served to hydrogenate
the longer carbon chain compounds to deoxygenated
hydrocarbons and maintain the catalyst’s activity by promoting
2
the formation of oxygen vacancies on ZrO . Without Cu,
oxygenated compounds adsorbed on the active sites of the
catalyst and eventually deactivated it, as observed with
experiments using only ZrO (Fig. S1, ESI†). The usage of Cu,
2
which is a relatively mild hydrogenation catalyst, also served to
minimize the premature hydrogenation of carboxylic acids.
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Upgrading of pure acetic acid
by Cu at these conditions. The ratio of propylene to propane
was ~20. Our usage of Cu prevented significant catalyst
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DOI: 10.1039/C9GC00513G
deactivation, but led to the production of some propylene.
However, propylene is a valuable α-olefin, making it an
interesting side reaction. Moreover, the majority of gas
hydrocarbons are olefins (including isobutylene, pentene and
hexene), with propylene being the predominant product (>50
mol% carbon of total gas). The high ratio of propylene to
propane, as well as being the major gas product, should
facilitate recovery downstream.
Interestingly, despite the presence of Cu as
a
hydrogenation catalyst, the proportion of alkanes and
cycloalkanes within the organic oil remained low (1.6 mol%
carbon). The prevalence of double bond functionalities was
also observed in the gas phase, with propylene being the
major product rather than propane. As reducible oxides such
as ZrO
2
have high affinity towards bonding oxygenate
is
functionalities, and since the interface between Cu and ZrO
2
1
8
known to be active for hydrogenation , most hydrogenation
sites were likely occupied by oxygenates, leading to limited
double bond hydrogenation. Similar hydrogenation inhibition
behavior with Cu was also observed in our previous work on
1
9
Fig. 3 Upgrading of pure acetic acid over 2g 2 wt% Cu/ZrO
. A) Molar carbon carboxylic acid upgrading to olefins.
2
-1
distribution of the product stream (T = 400 °C, P = 10 bar H
2
, WHSV = 0.3 h , H
2
Within the carbon distribution of the product stream, 59.6
mol% were C hydrocarbons or longer, 20.3 mol% was
propylene, likely produced through acetone hydrogenation,
and 7.1 mol% was unreacted acetone, indicating that the main
flow = 20 mL/min, conversion of acetone = 94.2 %, time on stream = 21.3 h).
Oxygenates consisted of oxygenated molecules in organic, aqueous and gas
phases. B) Acetone conversion, organic oil yield [wt%] and liquid hydrocarbon
yield as a function of time. Regeneration of the catalyst carried out at time on
6
stream = 167.6 h and 352.4 h. C) Molar carbon distribution of linear versus cyclic intermediate was likely acetone and subsequently mesityl
and aromatic compounds in the organic oil phase (time on stream = 21.3 h). D)
Molar carbon distribution of oxygenates versus hydrocarbons in the organic oil
phase (time on stream = 21.3 h).
oxide. Given the preponderance of aromatic molecules (Fig.
S2, S3 and Table S1, ESI†), ketonization/cascade aldol
condensations was the primary route in the upgrading of
acetic acid. To further study the mechanism, we varied the
We first carried out the upgrading of pure acetic acid as a
WHSV (Fig. S4, ESI†). Increasing the WHSV (i.e. decreasing the
2
model feed over 2 g of 2 wt% Cu/ZrO at a weight hourly space
residence time) increased the proportion of acetone in the
carbon distribution, while the number of products with a
higher carbon number decreased. Even at higher WHSVs,
acetic acid was not detected. These observations further
confirmed that ketonization/cascade aldol condensation was
the main reaction pathway, and that ketonization was
significantly faster than aldol condensation or hydrogenation
reactions, which were the rate limiting steps.
-1
velocity (WHSV) of 0.3 h . As mentioned, the process resulted
in a liquid product stream that spontaneously separated into
an organic oil phase and an aqueous phase, in addition to a gas
stream. Analysis of the molar carbon distribution of all three
phases (Fig. 3A) systematically showed complete conversion of
acetic acid. The majority of carbons in the liquid phases were
8 9
present in the form of C and C hydrocarbons. These
hydrocarbons primarily consisted of both aromatics (xylenes
and mesitylene) and cycloalkenes (dimethyl and trimethyl
cyclohexenes). Acetone, the main intermediate in the
upgrading route, represented 7.1 mol% carbon of the product
stream. Since acetic acid was completely converted but
acetone remained, we concluded that the cascade aldol
condensation/hydrogenation reactions were rate limiting. In
addition, other oxygenates, including ketones and phenols
were present in both organic and aqueous phases. Methyl
isobutyl ketone (MIBK) was detected, rather than mesityl
oxide. The low proportion of MIBK, coupled with no observed
mesityl oxide indicated that aldol condensation of products
longer than acetone had a higher rate at these reaction
conditions compared to hydrogenation.
However, the presence of molecules with carbon numbers
that were not multiples of three suggests that there are other
side reactions happening in addition to these simple cascade
reactions. Notably, acetic acid could react in other routes
(hydrogenation to acetaldehyde followed by condensation
reactions with molecules of a higher carbon number) and
higher hydrocarbons could also crack at high temperatures (or
release methane from tertiary carbons). These reactions are
not necessarily detrimental, as long as the subsequent
products have increased carbon chain length. Overall, a mass
yield of 23.7 wt% organic oil was obtained at these conditions.
The organic oil mass yield over a course of 150 h time on
stream was fairly constant (Fig. 3B), with minor fluctuations
probably due to error when handling smaller sample sizes.
Because acetic acid was completely converted, we tracked the
conversion of the main intermediate, acetone, to characterize
Over 20 mol% of carbon was converted to C
3
gaseous
hydrocarbons, which was likely due to acetone hydrogenation
4
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the stability of the catalyst. Over 150 h time on stream, the has six carbons, mesityl oxide only has a five cVaierwbAortnicleliOnnelianer
conversion of acetone dropped from 94.2 mol% to 86.7 mol%. backbone, rendering it unlikely undergDoOiI:n1t0r.a10m3o9/leCc9uGlCa0r05s1e3lfG-
However, the combined liquid hydrocarbon and oxygenates cyclization. This points to the proposed aldol condensation
yield in the organic oil phase only decreased from 34.8 mol% reaction pathway, as the majority of C compounds detected
6
to 30.8 mol%. The rest of the reduced conversion in acetone (MIBK) are linear/branched rather than cyclic/aromatic.
was reflected in a loss of propylene yield from 11.9 mol% to Overall, 75.1 mol% of the carbon in the organic oil was present
7
.4 mol%. Within the organic oil, the yield of liquid as cyclic or aromatic compounds (the molar carbon ratio of
hydrocarbons decreased from 26.1 mol% to 18.2 mol%. This monoaromatic to polyaromatic hydrocarbons was 15.3),
indicated that, not only did acetone conversion and organic oil demonstrating that cyclization was highly favored. Within
yield slightly decrease because of deactivation on the aldol hydrocarbons in the organic oil that are non-cyclic/aromatic,
condensation sites, but the liquid hydrocarbon and propylene branched compounds predominate (the molar carbon ratio of
yield also slightly decreased due to deactivation of the branched to linear hydrocarbons was 7).
hydrogenation sites of the catalyst.
An analysis of the oxygen content within the organic oil
showed that the oil consisted of mostly liquid hydrocarbons
Table 1 Characterization data for the two catalysts utilized in this study
(74.9 mol% carbon) rather than oxygenates (Fig. 3D). More
Catalyst
2 wt%
Cu/ZrO
1.74
7.92
106.97
3.4
0.072
200
290
0.5 wt%
2 wt% Cu/ZrO
(post-reaction)
2
importantly, the O/C ratio in the oil was decreased to 0.04,
compared to 1 for acetic acid and 0.33 for acetone. This 96%
removal of oxygen from acetic acid indicates that our
upgrading strategy is viable for producing deoxygenated oil
with high carbon numbers. Using the mass fractions of C, H
2
Cu/ZrO
0.52
2
Cu loading [wt%]
Cu dispersion [%]
BET surface area [m /g]
BJH pore size [nm]
BJH pore volume [cm /g]
Total acidity [µmol/g]
Total basicity [µmol/g]
1.68
-
30.72
7.1
0.069
92
59
7.00
102.37
3.4
0.081
290
296
2
and O within the identified compounds of the oil to estimate
3
20,21
the lower heating value (LHV),
we calculated that the
organic oil produced from our process had a LHV of 40.0
MJ/kg. As ASTM D1655 specifications for aviation fuel
2
2
stipulates a minimum net heat of combustion of 42.8 MJ/kg,
our organic oil would not affect the heat of combustion
significantly if utilized as a drop-in blend. Additionally, the C
Post-reaction characterization (Table 1) of the catalyst
showed a slight decrease in copper loading, likely due to
inaccuracies in recovering the entire mass of catalyst after
reaction. The surface area of the catalyst, total acidity and
basicity decreased while the pore size increased. However, the
pore volume remained the same. This indicated sintering of
the support, which was likely partially responsible for the slight
decrease in acetone conversion and organic oil yield. High-
angle annular dark-field scanning transmission electron
microscopy (HAADF-STEM) and energy-dispersive X-ray
spectroscopy (EDX) mapping of the catalyst (Fig. S5 and S6,
ESI†) showed that the catalyst recovered after reaction had
some drastically larger copper nanoparticles (30.8 – 93.0 nm
from 3.1 – 6.9 nm of the fresh catalyst), which demonstrated
that some irreversible deactivation was likely due to copper
sintering. This particular phenomenon was likely partially
responsible for the slight decrease in liquid hydrocarbon and
propylene yield.
8
to C15 range of compounds in the organic oil is similar to the
Regeneration of the catalyst (via calcination under
synthetic air at 500 °C, followed by reduction under H
2
at 450
°
C) restored some of the liquid hydrocarbon yield and acetone
conversion, with a second regeneration performing similarly.
Overall, the recovery of activity indicated that the deactivation
in the first run was partially reversible, with irreversible
deactivation likely due to initial copper and pore sintering,
followed by reversible coking on the aldol condensation and
hydrogenation sites (EDX mapping of the catalyst post-reaction
using SiN grids showed small quantities of deposited coke, Fig.
S6C and S6D, ESI†).
The carbon distribution of the organic oil phase showed
that most compounds were molecules with a carbon number
of eight or higher (79.1 mol% carbon) (Fig. 3C). Even though it
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carbon number distribution of kerosene-type aviation fuel (C
Journal Name
8
-
Interestingly, the carbon distribution in the liquid phase
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2
3
DOI: 10.1039/C9GC00513G
8 9 9
C16). The high aromatic content of the oil (Fig. S7A, ESI†) also hydrocarbon mixture shifted from primarily C and C to C and
makes it suitable for use as an additive for conventional jet
C10 hydrocarbons, which was also observed with 0.5 wt%
fuel (in addition to the high ratio of monoaromatic to Cu/ZrO
2
with pure acetic acid (Fig. S10, ESI†). We attributed
polyaromatic hydrocarbons), which influences critical this phenomenon to the lower copper loading of the catalyst.
parameters such as lubricity, density and the swelling Because of the lower hydrogenation rate, more oxygenated
2
4
behaviour of elastomer seals in jet turbines. The presence of molecules underwent aldol condensation reactions to reach
phenols in our organic oil could also be beneficial as an higher carbon numbers before being hydrogenated to liquid
2
2
antioxidant additive for jet fuel.
Upgrading of dilute & biomass-derived acetic acid
As production of glacial acetic acid is difficult in industrial obtained at 0.5 wt% Cu/ZrO
hydrocarbons. This shift was also observed when a higher
-1
2
WHSV (2.4 h ) was used with 2 wt% Cu/ZrO (Fig. S4, ESI†),
where the carbon distribution resembled the results we
2
.
processes, we explored the use of this process with a diluted
acetic acid feed. To this end, we applied this upgrading route excess hydrogen), hydrogenation likely acted like a pseudo-1
As mentioned earlier, at our reaction conditions (with
st
for an aqueous feed of 50 wt% acetic acid.
order reaction, while aldol condensation acted like a pseudo-
nd
nd
Because aldol condensation is a pseudo-2 order reaction
2
order reaction. At low acetone conversion, aldol
st
while hydrogenation is a pseudo-1 order reaction due to the condensation was faster than at higher conversion due to the
excess hydrogen that is present in this case, utilization of the higher acetone concentration. But as acetone was consumed
2
same 2 wt% Cu/ZrO catalyst resulted in a large proportion of and the amount of water from condensation increased, the
acetone hydrogenation to propylene (Fig. S8, ESI†). Due to this concentration of all substrates (including acetone) decreased,
difference in kinetics, the relative rate of aldol condensation which likely caused the rate of aldol condensation to decrease
rapidly decreased with decreasing acetone concentrations, faster than the rate of hydrogenation. For this reason, at high
compared to hydrogenation. This relative increase in the rate WHSV (lower acetone conversion), we observed more
of hydrogenation could be compensated by decreasing the condensation products vs. hydrogenation products than at
metal loading. Therefore, we used a catalyst for upgrading the lower WHSV. This was also corroborated by the decreased
dilute acetic acid feed that had a lower copper loading (0.5 amount of propylene (a product of acetone hydrogenation) at
wt%) compared to previous experiments (2 wt%).
high WHSV. We observed a similar shift to a higher proportion
of C and C10 products with lower H partial pressure, which
similarly decreased hydrogenation vs. condensation rates
albeit through a different mechanism (Fig. S9, ESI†).
2
Fig. 4 Upgrading of 50 wt% aqueous acetic acid over 2g 0.5 wt% Cu/ZrO . A)
9
2
2
Molar carbon distribution of the product stream. (T = 400 °C, P = 10 bar H ,
-1
2
WHSV = 0.3 h , H flow = 20 mL/min, conversion of acetone = 59.2 %, time on
stream = 265.3 h) Oxygenates consisted of oxygenated molecules in organic,
aqueous and gas phases. B) Molar carbon distribution of linear versus cyclic and
aromatic compounds in the organic oil phase. (time on stream = 265.3 h) C)
Molar carbon distribution of oxygenates versus hydrocarbons in the organic oil
phase for a 50 wt% aqueous acetic acid model feed and 40.3 wt% biomass-
derived acetic acid feed. (time on stream for model feed = 265.3 h, time on
stream for biomass-derived feed = 76.3 h).
Our analysis of the organic oil phase (Fig. 4B) shows that
the majority of carbon was present as cyclic/aromatic C
8 9
, C
and C10. Aside from the higher proportion of C linear
3
compounds (mainly acetone) and the increase in C10, the rest
of the cyclic/aromatic distribution in the organic oil remained
similar to reactions with pure acetic acid and 2 wt% copper,
with a cyclic/aromatic proportion of 76.5 mol% carbon. Within
the organic oil, the molar carbon ratio of monoaromatic to
polyaromatic hydrocarbons was 33.9, and branched to linear
hydrocarbons was 57.5. The mass yield of the organic oil was
At these reaction conditions, the conversion of acetone
was reduced to 59.2 % (Fig. 4A), which was due to the
decrease of the aldol condensation rate that accompanied the
decrease in reactant concentration with increased water
content. The high amount of unreacted acetone further
justified the use of a lower copper loading, as a higher copper
loading would have preferentially hydrogenated the acetone
2
1.2 wt%, and consisted of 61.3 mol% carbon liquid
hydrocarbons (Fig. 4C). While this was lower compared to
previous experiments, further optimization on the WHSV could
increase acetone conversion towards liquid hydrocarbons.
Nevertheless, this indicates the possibility of upgrading
aqueous acetic acid, which is important for biomass-derived
feedstock.
to C
hydrocarbons (10.6 mol% carbon) was lower compared to 2
wt% Cu/ZrO with pure acetic acid (20.3 mol% carbon), and
much lower compared to 2 wt% Cu/ZrO with diluted acetic
acid (34.5 mol% carbon). We also performed runs with pure
acetic acid with 2 wt% Cu/ZrO and 1 bar H partial pressure
10 vol% H in Ar) which showed similar behaviour (Fig. S9,
3 3
gas hydrocarbons. In this case, the proportion of C gas
2
2
To demonstrate this applicability to real biomass-derived
streams, we used the same catalyst and conditions to upgrade
2
2
4
0.3 wt% aqueous acetic acid that was produced from steam-
(
2
exploded beech wood (see ESI† for detailed separation and
concentration protocol). The resulting organic oil had a similar
molar carbon distribution (the molar carbon ratio of
monoaromatic to polyaromatic hydrocarbons was 37.4, and
branched to linear hydrocarbons was 42.1) compared to the
reaction with model feed (Fig. 4C), with the only noticeable
difference being a small decrease in the yield of C10
ESI†), but the catalyst deactivated rapidly, likely due to the
insufficient regeneration of oxygen vacancies by molecular
hydrogen. The decrease in the aldol condensation rate due to
higher water content was also partially mitigated by the
increase in total acidity and basicity of 0.5 wt% Cu/ZrO
compared to 2 wt% Cu/ZrO (Table 1), as aldol condensation
reactions are catalyzed by both acid and basic sites.
2
2
1
0
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hydrocarbons accompanied by a corresponding increase in the Upgrading of dilute & biomass-derived acetic/butanoic acid
View Article Online
DOI: 10.1039/C9GC00513G
9
yield of C hydrocarbons. The yield of organic oil was also
reduced to 15.4 wt%. Both observations could be due to the
increase in the water content of the feedstock, which might
have lowered the rate of aldol condensation. Due to limited
quantities of biomass-derived acetic acid, the stability of the
catalyst was not investigated. However, given the very high
purity of the carboxylic acids (aside from water being present)
obtained by distillation, we do not anticipate significant
catalyst poisoning issues. Overall, these results demonstrated
the possibility of upgrading biomass-derived acetic acid
produced during pretreatment to liquid hydrocarbons.
The O/C content of the organic oil was reduced to 0.07 for
the model acetic acid feed and 0.06 for the biomass-derived
acetic acid feed. This content was slightly higher compared to
the 0.04 O/C ratio of the oil from pure acetic acid upgrading,
probably due to the decreased rate of hydrogenation as a
result of our decision to use a lower copper loading.
Nevertheless, this corresponds to a 93% and 94% removal of
oxygen from model and biomass-derived acetic acid,
respectively. We similarly estimated the LHV of the organic oil
and found 38.3 MJ/kg for model acetic acid and 37.7 MJ/kg
from biomass-derived acetic acid. These values are lower
compared to the LHV of oil obtained from pure acetic acid,
which could be due to the small increase in O/C ratio.
Nevertheless, optimization of the reaction conditions could
increase the proportion of deoxygenation which would likely
increase the LHV of the oil to values similar to those obtained
from pure acetic acid. Furthermore, the shift towards carbon
9
numbers of primarily C and C10 in the upgrading of diluted
acetic acid (Fig. S7B and S7C, ESI†) meant that the resulting oil
could have a higher distillation curve that would be more
comparable with a commercial aviation fuel blending agent.
mixtures
Fig. 5 Upgrading of 28/12 wt% aqueous acetic/butanoic acid over 3g 0.5 wt%
Cu/ZrO . A) Molar carbon distribution of the product stream. (T = 400 °C, P = 10
bar H , WHSV = 0.2 h , H
2
-1
2
2
flow = 20 mL/min, time on stream = 72.1 h)
Oxygenates consisted of oxygenated molecules in organic, aqueous and gas
phases. B) Molar carbon distribution of linear versus cyclic and aromatic
compounds in the organic oil phase. (time on stream = 72.1 h) C) Molar carbon
distribution of oxygenates versus hydrocarbons in the organic oil phase for 28/12
wt% aqueous acetic/butanoic acid model feed and 28/12 wt% biomass-derived
acetic/butanoic acid. (time on stream for model feed = 72.1 h, time on stream
for biomass-derived feed = 66.2 h)
We also performed cross-ketonization of acetic and butanoic
acid to further increase the average carbon number of the
organic oil (Fig. 5A). An initial model feed of 28/12 wt%
aqueous acetic/butanoic acid feed was used, which
corresponded to a 7:3 mass ratio of acetic acid to butanoic
acid.
Similarly to direct ketonization of acetic acid, full
conversion of carboxylic acids was reached. Ketonization
products were once again important intermediates, with a
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J. Name., 2013, 00, 1-3 | 7
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ARTICLE
Journal Name
large majority of 2-pentanone, which formed most of the along with a secondary fermentation (Fig. 6, seVeiewEASrtIi†clefOonrlinae
oxygenated molecules in the product stream. The significant description of the process and the subDsOeIq: u10e.1n0t39p/uCr9iGfiCca00ti5o1n3G).
amount of this product suggested that cross-ketonization was This enabled us to use three fractions of lignocellulosic
heavily favored compared to homoketonization. This result biomass (cellulose, hemicellulose and acetate) in our
-1
was obtained with a reduced WHSV of 0.2 h , because longer upgrading route.
chain ketones were slower to condense and required longer
In this case, the oil mass yield was 16.0 wt%, which was
residence time to reach reasonable conversions. As with direct similar to the yield obtained when utilizing model feed (Fig.
ketonization of acetic acid, compounds in the organic oil that 5C). However, the molar carbon distribution within the organic
8
were longer than C were mainly cyclic/aromatic compounds oil showed a higher proportion of liquid hydrocarbons (57.2
(52.6 mol% carbon) (Fig. 5B). The molar carbon ratio of mol% carbon). The molar carbon ratio of monoaromatic to
monoaromatic to polyaromatic hydrocarbons was 85.2, and polyaromatic hydrocarbons was 127.6, and branched to linear
branched to linear hydrocarbons was 1.4. The decrease in the hydrocarbons was 2.7, which was similar to the model feed.
ratio of branched to linear hydrocarbons could be due to the We also measured
a comparable amount of liquid
presence of pentene and heptene in the organic oil, which hydrocarbons that had a carbon chain length of C11 or more
further indicated the favoring of cross-ketonization (previously (21.0 mol% carbon) demonstrating that our catalytic platform
with only acetic acid, hydrogenation of the main intermediate can be used to produce a deoxygenated oil from real bio-
acetone produced propylene in the gas phase, rather than derived carboxylic acid mixtures.
pentene in the organic oil, which was produced from
pentanone).
An analysis of the compounds within the organic oil
showed that the O/C content was 0.09 for the model feed and
The mass yield of the organic oil was 17.8 wt% compared 0.07 for the biomass-derived feed. This compared favorably
to the original acids in the feed. Within the organic oil phase, with the O/C content of oil produced with pure or diluted
4
4.5 mol% carbon were liquid hydrocarbons (Fig. 5C). Despite acetic acid. From the initial O/C ratio of 0.82 (1 for acetic acid
a lower WHSV, the liquid hydrocarbon proportion was still and 0.5 for butanoic acid), our upgrading process resulted in
lower compared to direct ketonization of acetic acid, an 88% removal of oxygen for the model feed and 91%
confirming that ketones with a longer carbon chain length had removal for the biomass-derived feed. LHV estimates indicated
a lower rate of aldol condensation. Because of their increased a value of 37.5 MJ/kg for the model feed and 38.5 MJ/kg for
carbon length, a higher amount of product was retained in the the biomass-derived feed, similarly to the values estimated for
organic oil rather than the aqueous phase. Importantly, liquid diluted acetic acid feeds. In the case of cross-ketonization, the
hydrocarbons containing eleven carbons or above constitute larger fraction of carbon present as C11 compounds and above
1
2.3 mol% carbon of the organic oil, compared to 4.5 mol% (Fig. S7D and S7E, ESI†) might further benefit the properties of
carbon with direct ketonization. This larger fraction of longer our oil for use as an aviation fuel blending.
carbon chain products demonstrated that cross-ketonization
Aviation fuel testing of organic oil as an additive
of acetic acid with butanoic acid can indeed increase the
average carbon number of the organic oil, albeit at the To demonstrate the viability of the produced organic oil as an
expense of total liquid hydrocarbon yield. This chain additive for aviation fuels, typical aviation fuel parameters
lengthening showed that the products of the catalytic were tested for the organic oil produced from pure
reactions can be tuned by the properties of the feedstock that commercial acetic acid. The process was upscaled to 20 g of 2
-1
2
wt% Cu/ZrO at the same WHSV of 0.3 h in order to produce
enough organic oil in a reasonable amount of time. The
composition of the organic oil was verified to be similar to the
organic oil that was produced at a smaller scale (Fig. S11, ESI†).
The purity of the organic oil should be similar to organic oil
obtained from biomass-derived acetic acid, as our purification
procedure (see ESI† for the procedure) involved distillation of
the acids, removing any detectable trace of biomass-derived
is produced biologically.
Fig. 6 Steam-explosion of beech wood, followed by consolidated bioprocessing impurities. Prior to fuel testing, we also performed inductively
and secondary fermentation of the resulting polysaccharides to obtain biomass-
derived acetic and butanoic acid.
coupled plasma-mass spectrometry (ICP-MS) measurements
on the organic oil, and found metal leaching products such as
Cu, Fe and Cr to be below detection limits (Cu and Cr < 0.07
To demonstrate this concept further, we used this cross-
ppm, Fe < 0.68 ppm).
ketonization and aldol condensation platform to upgrade a
A blend of 10 vol% organic oil with Jet A-1 fuel was tested,
mixture of acetic and butanoic acid produced from beech
in accordance with the test methods of the Aviation Fuel
wood. The acetic acid was obtained from steam-explosion of
Quality Requirements for Jointly Operated Systems (AFQRJOS):
the beech wood, similarly to our experiments above with real
acetic acid feeds. After the acetate fraction was removed, the
remaining polysaccharides were used to produce butanoic acid
in a consolidated bioprocess based on a microbial consortium
25
Issue 29 – Oct 2016 for Jet A-1 , which encompasses the
British Ministry of Defence Standard DEF STAN 91-091/Issue 9
and the ASTM Standard Specification D1655-16a. The test
8
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parameters include aromatic content, sulfur content, density,
specific energy and the distillation curve (Table 2).
Using this method, the valorization of acetate, which is an
often neglected fraction of biomass, can contribute to and
View Article Online
DOI: 10.1039/C9GC00513G
expand the carboxylate platform that is based on producing
carboxylic acids from biomass-derived polysaccharides.
Maximizing the use of these different biomass fractions and
producing drop in fuels for industries like aviation, where no
other sustainable alternatives are currently available, will
increase the chances of deploying efficient and profitable
biorefineries.
Table 2 Aviation fuel testing results for a 10 vol% blend of organic oil with Jet A-1
Limita
Property
Aromatics [vol%]
Sulfur, total [wt%]
Distillation (101.3 kPa)
Initial boiling point [°C]
Test value
18.3
0.032
Test method
ASTM D1319
ASTM D5453
<25.0
<0.30
64
-
<205.0
-
-
-
<300
<1.5
<1.5
1
2
5
9
0 vol% recovered [°C]
0 vol% recovered [°C]
0 vol% recovered [°C]
0 vol% recovered [°C]
165
171
189
230
267
0.8
ASTM D86
Conflicts of interest
There are no conflicts to declare.
End point [°C]
Residue [vol%]
Loss [vol%]
0.2
7
8
75.0 –
40.0
>42.8
Acknowledgements
This work was supported by the Swiss National Science
Foundation (SNSF) under the National Research Program 70:
Density at 15 °C [kg/m3]
801.1
43.2
ASTM D4052
ASTM D3338
Specific energy, net [MJ/kg]
a
As established by AFQRJOS. Limits which do not have a value are only required Energy Turnaround program (nb: 407040_153866 and
to report their measured values.
4
07040_153868). This work was also performed in the
framework of the Swiss Competence Center for Bioenergy
Research (SCCER-BIOSWEET) through the Swiss Commission
for Technology and Innovation grant KTI.2014.0116 and by
EPFL. We thank Prof. John Ralph (University of Wisconsin -
Madison) for discussions on the structure of acetate in
lignocellulosic biomass, which were the basis for Chart 1. We
thank the EPFL Central Environmental Laboratory for the ICP-
MS analyses.
The blended jet fuel had 18.3 vol% aromatics, showing that
while the organic oil is composed predominantly of aromatics,
it is still suitable to be used as an additive. The sulfur content,
density and distillation curve were all within the specifications
imposed by AFQRJOS. More importantly, the net specific
energy was 43.2 MJ/kg, demonstrating a low oxygen content.
Overall, this indicated that our upgrading strategy has the
potential to be used for the production of an aviation fuel
additive from carboxylic acids.
Notes and references
1
2
3
J. S. Luterbacher, D. M. Alonso and J. A. Dumesic, Green Chem.,
014, 16, 4816–4838.
A. M. Johnson, H. Kim, J. Ralph and S. D. Mansfield, Biotechnol.
Biofuels, 2017, 10, 48.
L. Shuai, M. T. Amiri, Y. M. Questell-Santiago, F. Héroguel, Y. Li,
H. Kim, R. Meilan, C. Chapple, J. Ralph and J. S. Luterbacher,
Science, 2016, 354, 329–333.
L. Shuai, M. Talebi Amiri and J. S. Luterbacher, Curr. Opin. Green
Sustain. Chem., 2016, 2, 59–63.
Conclusions
2
In summary, we presented a single step catalytic platform for
valorizing the acetate and carboxylate fractions produced from
lignocellulosic biomass to jet fuel additives. Model feeds were
used initially, which facilitated the identification of the optimal
catalyst and process conditions. We then notably
demonstrated that real biomass-derived streams of short-
chain carboxylic acids can be upgraded to aromatics and
cycloalkenes of eight carbon or higher in a single step.
Specifically, aqueous streams of acetic acid and butanoic acid
produced from steam pretreatment and subsequently
consolidated bioprocessing of the pretreated beech wood
were utilized. The resulting organic oil consisted of mainly
aromatics and cycloalkenes, with compositions and heating
values suitable to be used as additives for aviation fuel, which
were further confirmed via aviation fuel testing. The results
from both model and biomass-derived feed were similar, with
minor differences attributed to slight changes in processing
conditions (eg. initial water content). Our use of real biomass-
derived feed highlights the viability of this platform, as real
feeds typically present more challenges (low initial
concentrations and biomass related impurities which
necessitates concentration and purification) not encountered
with model feeds.
4
5
6
S. J. Dee and A. T. Bell, ChemSusChem, 4, 1166–1173.
S. K. R. Patil and C. R. F. Lund, Energy Fuels, 2011, 25, 4745–
4
755.
7
8
9
P. Thanakoses, A. S. Black and M. T. Holtzapple, Biotechnol.
Bioeng., 2003, 83, 191–200.
S. Taco Vasquez, J. Dunkleman, S. K. Chaudhuri, A. Bond and M.
T. Holtzapple, Biomass Bioenergy, 2014, 62, 138–148.
M. T. Holtzapple, R. R. Davison, M. K. Ross, S. Aldrett-Lee, M.
Nagwani, C.-M. Lee, C. Lee, S. Adelson, W. Kaar, D. Gaskin, H.
Shirage, N.-S. Chang, V. S. Chang and M. E. Loescher, Appl.
Biochem. Biotechnol., 1999, 79, 609–631.
0 T. N. Pham, T. Sooknoi, S. P. Crossley and D. E. Resasco, ACS
Catal., 2013, 3, 2456–2473.
1 T. N. Pham, D. Shi, T. Sooknoi and D. E. Resasco, J. Catal., 2012,
1
1
1
2
95, 169–178.
2 A. J. Crisci, H. Dou, T. Prasomsri and Y. Román-Leshkov, ACS
Catal., 2014, 4, 4196–4200.
This journal is © The Royal Society of Chemistry 20xx
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ARTICLE
Journal Name
1
1
1
1
1
1
3 M. Gliński, J. Kijeński and A. Jakubowski, Appl. Catal. Gen., 1995,
28, 209–217.
4 T. Prasomsri, T. Nimmanwudipong and Y. Román-Leshkov,
Energy Environ. Sci., 2013, 6, 1732–1738.
View Article Online
DOI: 10.1039/C9GC00513G
1
5 F. G. Klein and J. T. Banchero, Ind. Eng. Chem., 1956, 48, 1278–
1
286.
6 G. S. Salvapati, K. V. Ramanamurty and M. Janardanarao, J. Mol.
Catal., 1989, 54, 9–30.
7 E. R. Sacia, M. Balakrishnan, M. H. Deaner, K. A. Goulas, F. D.
Toste and A. T. Bell, ChemSusChem, 2015, 8, 1726–1736.
8 I. Ro, Y. Liu, M. R. Ball, D. H. K. Jackson, J. P. Chada, C. Sener, T.
F. Kuech, R. J. Madon, G. W. Huber and J. A. Dumesic, ACS
Catal., 2016, 6, 7040–7050.
1
9 J. H. Yeap, F. Héroguel, R. L. Shahab, B. Rozmysłowicz, M. H.
Studer and J. S. Luterbacher, ACS Catal., 2018, 8, 10769–10773.
0 S. A. Channiwala and P. P. Parikh, Fuel, 2002, 81, 1051–1063.
1 ASTM D4809-18: Standard Test Method for Heat of Combustion
of Liquid Hydrocarbon Fuels by Bomb Calorimeter (Precision
Method), ASTM International, West Conshohocken, PA, 2018.
2 ASTM D1655-18a: Standard Specification for Aviation Turbine
Fuels, ASTM International, West Conshohocken, PA, 2018.
3 G. Hemighaus, T. Boval, J. Bacha, F. Barnes, M. Franklin, L. Gibbs,
N. Hogue, J. Jones, D. Lesnini, J. Lind and J. Morris, Aviation
Fuels Technical Review (FTR-3), Chevron Products Company,
2
2
2
2
2
007.
2
2
4 I. A. Al-Nuaimi, M. Bohra, M. Selam, H. A. Choudhury, M. M.
El-Halwagi and N. O. Elbashir, Chem. Eng. Technol., 2016, 39,
2
217–2228.
5 Aviation Fuel Quality Requirements for Jointly Operated Systems
AFQRJOS): Issue 29 - Oct 2016, Joint Inspection Group (JIG),
016.
(
2
1
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30
Oxygenates
PagOe 11 of 11 Green Chemistry
Hydrocarbons
OH
20
Acetic acid
and/or
O
10
OH
Butanoic acid
0
Carbon number
Single step upgrading of biomass-derived short carboxylic acids
to a jet fuel additive