Article
pubs.acs.org/EF
Cite This: Energy Fuels 2019, 33, 3275−3289
Impact of Alternative Fuel Blending Components on Fuel
Composition and Properties in Blends with Jet A
Petr Vozka,† Dan Vrtiška,‡ Pavel Š imać ě k,‡ and Gozdem Kilaz*,†
†
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School of Engineering Technology, Fuel Laboratory of Renewable Energy, Purdue University, West Lafayette, Indiana 47906,
United States
‡
Department of Petroleum Technology and Alternative Fuels, University of Chemistry and Technology, 16628 Prague 6, Czech
Republic
S Supporting Information
*
ABSTRACT: One challenge in the deployment of alternative aviation fuels is the lengthy “fuel approval process”, which costs
millions of dollars and can take many years as the exact effect of these alternative options on engine and framework is still an
unknown. A candidate aviation fuel needs to pass the tests as deemed necessary by the ASTM D4054 Standard Practice. The
fuel manufacturer faces the risk of not receiving the ASTM certification after significant financial and time investment, which
currently acts as a considerable hindrance to broadening the alternative aviation fuel options in commercial and military aircraft.
Approval tests are based on the fuel properties and fuel performance as there is currently a knowledge gap on fuel chemical
composition−property correlations. Therefore, the aim of this study was to accomplish the first step in this target, i.e., to obtain
a detailed chemical composition of four approved blending components (FT-SPK, HEFA, SIP, and ATJ) and their mixtures
with Jet A using GC × GC-TOF/MS and GC × GC-FID. Infrared spectroscopy and principal components analysis were
utilized as additional techniques to demonstrate the differences among the blending components and Jet A, further utilizing
their infrared spectral features. Moreover, the main physiochemical properties were measured, such as distillation profile,
density, viscosity, flash point, freezing point, and net heat of combustion. Lastly, the impact of the differences in chemical
composition on these main fuel properties was discussed.
■
INTRODUCTION
The data developed from the ASTM D4054 process is
included in “Research Reports” used to support consensus
ballots to add alternative fuels to ASTM D7566, separated by
production process (as opposed to feedstock). Fuels are added
as annexes, with ASTM D7566 currently containing five
approved annexes, as shown in the Table 1 below.
Currently, the Research Reports provide detailed information on five nonpetroleum-source-derived blending components for their use in jet fuel.2 Fischer−Tropsch hydroprocessed synthesized paraffinic kerosene (FT-SPK) was
certified as the first nonpetroleum-originated synthetic
blending component for civil jet fuels in 2009. According to
the limitations defined in ASTM D7566, FT-SPK may only be
used after blending up to a maximum ratio of 50 vol % with the
conventional jet fuels. Current commercial plants that produce
synthetic jet fuels and fuel blending components via FT
technology utilize only coal (e.g., Sasol IPK) and natural gas
(e.g., Syntroleum S-8, Shell GTL) as the feedstock. As biomass
has not yet been utilized as one of the feedstocks, alternative
jet fuels manufactured via FT technology does not reduce the
carbon footprint of air transportation even though FT offers a
nonpetroleum pathway.3,4 Synthesized paraffinic kerosene
from hydroprocessed esters and fatty acids (HEFA) is
currently the second nonpetroleum blending component
approved by ASTM in 2011. Content of HEFA in jet fuels is
There are three main governing ASTM standards with regards
to aviation fuel certification and deployment, namely, ASTM
D1655 (Aviation Turbine Fuels), D7566 (Aviation Turbine
Fuel Containing Synthesized Hydrocarbons), and D4054
(Evaluation of New Aviation Turbine Fuels and Fuel
Additives). D1655 is the protocol for petroleum-derived
aviation fuels, while D7566 focuses on the alternative options.
All candidate alternative aviation fuels have to be evaluated
through an approval process D4054, which is composed of four
main tiers of testing, i.e., (i) fuel specification properties, (ii)
fit-for-purpose properties, (iii) components tests, and (iv)
engine test. Tier 1 testing should be performed on the
candidate fuel as well as on the final blend.1 Here, it should be
noted that none of the fuel candidates submitted to ASTM
were approved without further blending with petroleum-based
jet fuels; hence, it is referred to as a “synthetic blending
component”. Based on the results from tier 1 testing, the
Original Equipment Manufacturers (OEMs) will suggest on
which additional test should be performed in tiers 2, 3, and 4.
Once the blending component is approved, it is included in
D7566 standard along with the maximum blending ratio.
Approved fuels are then recertified as ASTM D1655. The
reason that the approval process does not lead directly to
ASTM D1655 is that ASTM D7566 imposes stricter limits on
the alternative fuels and blends as a risk reduction measure.
Those limits were not intended to apply to conventional
(petroleum-derived) aviation fuels.
© 2019 American Chemical Society
Received: January 10, 2019
Revised: February 27, 2019
Published: March 6, 2019
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Table 1. Annexes A1-A5 from D7566
annex
A1
A2
A3
A4
A5
title
Fischer−Tropsch Hydroprocessed Synthesized
Paraffinic Kerosine (SPK)
Synthesized Paraffinic Kerosine from Hydroprocessed Esters and Fatty Acids (HEFA)
Synthesized Iso-Paraffins from Hydroprocessed
Fermented Sugars (SIP)
Synthesized Kerosine with Aromatics Derived by
Alkylation of Light Aromatics from Nonpetroleum Sources (SPK/A)
Alcohol-to-Jet Synthetic Paraffinic Kerosene
(ATJ-SPK)
approved
blend ratio
(vol %)
production process
Paraffins and olefins derived from synthesis gas via the Fischer-Tropsch (FT) process using iron or
cobalt catalyst.
Synthetic blend components shall be comprised of hydroprocessed synthesized paraffinic kerosine
wholly derived from paraffins derived from hydrogenation and deoxygenation of fatty acid esters
and free fatty acids.
Synthetic blend components shall be comprised of hydroprocessed synthesized iso-paraffins wholly
derived from farnesene produced from fermentable sugars.
SPK/A synthetic blending component shall be comprised of FT SPK as defined in annex A1
combined with synthesized aromatics from the alkylation of non-petroleum derived light
aromatics (primarily benzene).
ATJ-SPK synthetic blending components shall be comprised of hydroprocessed synthesized
paraffinic kerosene wholly derived from ethanol or isobutanol processed through dehydration,
oligomerization, hydrogenation, and fractionation.
50
50
10
50
50
of the correlations between chemical composition and
physiochemical properties of jet fuels containing various
synthetic blending components is an excellent feedback
mechanism for fuel producers. The manufacturers would be
equipped with the knowledge of the components necessary
and not as needed, which in turn enables fine-tuning of the
process. Consecutively, the carbon footprint of the fuel
production process can be significantly lowered.
Simultaneously, such knowledge is also important for
development of analytical methods suitable for identification
and determination of these synthetic components in
petroleum-based jet fuels. The content of approved synthetic
components is limited by the limits mentioned in Table 1, but
currently there is no reliable analytical method for their
identification and determination. In other words, it is very
difficult to measure the content of synthetic components in jet
fuel. An added benefit would be to enable a reliable supplierend user relationship due to a different price between jet fuels
and blending components. Vrtiška et al.32 focused on the
development of a method for determination of HEFA content
in HEFA/Jet A blends. The procedure was based on FTIR and
partial least-squares regression. The results of this study also
showed the possible use of principal component analysis
(PCA) to differentiate HEFA from Jet A according to the
infrared spectral features.
In our previous work,17 three different HEFA fuels produced
from different feedstocks (camelina, tallow, and mixed fat)
were compared based on their chemical composition and the
changes in their properties upon blending with Jet A. In this
work, chemical composition and fuel properties (distillation
profile, density, viscosity, flash point, freezing point, and net
heat of combustion) of additional approved alternative
blending components (FT-IPK, SIP, and ATJ) were measured
and compared. HEFA produced from camelina was also used
in this study for comparison purposes. This work contains
detailed chemical analyses of the blending components
mentioned above obtained from GC × GC-TOF/MS and
FID. Infrared spectroscopy and PCA were utilized in this study
as simple procedures to show differences in the chemical
composition of the blending components and Jet A and
provide an additional tool for the identification of mixtures of
blending components and Jet A.
limited to 50 vol %. In principle, any vegetable oil, animal fat,
or used cooking oil can be utilized as an HEFA feedstock (e.g.,
camelina, tallow, reprocessed tallow, mixed fat, etc.).5 The
third blending component is synthesized iso-paraffins (SIP)
from hydroprocessed fermented sugars which was approved in
2014. SIP is limited in jet fuels to 10 vol %. The fourth
component, synthesized paraffinic kerosene with aromatics
(FT-SPK/A), was added in 2015, and its content in jet fuels is
limited to 50 vol % in the U.S.; however, it can be used as a
neat (100%) jet fuel in Europe according to the DEF STAN
91-91.6 The fifth synthetic component, alcohol-to-jet (ATJ)
synthetic paraffinic kerosene, was added in 2016 and was
limited in jet fuels to 30 vol % until April 2018 with butanol as
a feedstock. Later, companies such as LanzaTech and Byogy
Renewables have worked on approval for a process with
ethanol as a feedstock. These companies, together with Gevo,
submitted data to ASTM International. This effort not only
resulted in the approval of ethanol as a feedstock but also
succeeded in increasing the ATJ maximum blending ratio from
30 to 50 vol %.4 The ATJ process, also called alcohol
oligomerization, is typically a three-step process, i.e., alcohol
dehydration, oligomerization, and hydrogenation. A wide range
of biomass can be used as a feedstock (e.g., corn, unrefined
sugars, switchgrass, corn stovers, corn fiber, etc.), and
additional details are described in the literature as well as for
other nonpetroleum fuel conversion technologies.7 The
blending limits of all synthetic components in jet fuel are
given in D7566; however, each final blend has to meet all
quality requirements specified in the D1655 standard.8
Several studies and reports discuss the chemical composition
and/or physiochemical properties of these components,
namely, FT-SPK,9−13 HEFA,5,11−17, SIP,9,10,12,18,19 and
ATJ;5,9,12,13,20 however, none of them attempt to correlate
them. Additionally, a few studies have focused on the
prediction of several properties from the chemical composition. One portion of these studies represented jet fuel chemical
composition by only three main hydrocarbon classes (nparaffins, aromatics, and branched + cyclic paraffins) measured
via NMR and/or HPLC.21−25 Other researchers used near
IR26 or GC-MS27,28 together with chemometric modeling or
artificial neural networks. Other studies29−31 have used
detailed chemical composition obtained from a comprehensive
two-dimensional gas chromatography (GC × GC) equipped
with time-of-flight mass spectrometry (TOF/MS) and a flame
ionization detector (FID). These studies can serve as
additional sources for understanding how the properties are
affected by chemical composition. A thorough understanding
■
EXPERIMENTAL SECTION
Materials. The petroleum-derived jet fuel Jet A (POSF 9326),
Fischer−Tropsch iso-paraffinic kerosene (FT-IPK) produced by Sasol
with coal as the feedstock (POSF 7629), hydroprocessed esters and
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Table 3. Chromatographic Conditions for GC × GC-TOF/
MS and GC × GC-FID
fatty acids (HEFA) produced by Honeywell UOP with camelina as
the feedstock (POSF 10301), and alcohol-to-jet synthetic paraffinic
kerosene (ATJ) produced by Gevo with butanol from microorganisms
as the feedstock (POSF 11498) were provided by Wright-Patterson
Air Force Base, Dayton, Ohio. Synthesized iso-paraffins from
hydroprocessed fermented sugars (SIP) produced by Amyris Inc.
with sugar cane as the feedstock were donated by the Aircraft Rescue
and Firefighting subdivision of the Federal Aviation Administration,
Egg Harbor Township, New Jersey. For this study, mixtures with
varying concentrations of fuel blending component (FT-IPK, HEFA,
SIP, ATJ) in Jet A were prepared (Table 2). There were also mixtures
GC × GC
TOF/MS
analytical
column
carrier gas
oven
temperature
modulation
period
offsets
secondary oven: 10 °C; modulator: 70 °C
temperatures
inlet: 280 °C; transfer line: 300 °C
solvent
n-pentane (+99% pure, Acros Organics), 300 s delay
GC × GC-FID
description
Table 2. Mixture Compositions and Designations
Jet A
(vol %)
blending component
(vol %)
100
95
90
0
5
10
85
80
70
60
50
15
20
30
40
50
40
60
FT-IPK
HEFA
SIP
FT-IPK HEFA
SIP
−
−
SIP 5
FT 10
HEFA 10 SIP
10a
−
−
SIP 15
FT 20
HEFA 20 −
FT 30
HEFA 30 −
FT 40
HEFA 40 −
FT 50a HEFA
−
50a
FT 60
HEFA 60 −
description
primary: Rxi-17Sil MS Restek (60 m × 0.25 mm × 0.25
μm); secondary: Rxi-1 ms Restek (1.4 m × 0.25 mm ×
0.25 μm)
UHP helium, 1.25 mL/min
isothermal 40 °C for 0.2 min, followed by a linear gradient
of 1 °C/min to a temperature 200 °C being held
isothermally for 5 min
4.0 s with 0.67 s hot pulse time
ATJ
ATJ
−
ATJ 10
analytical
column
−
ATJ 20
ATJ 30
ATJ 40
ATJ
50a
ATJ 60
carrier gas
oven
temperature
modulation
period
offsets
temperatures
solvent
a
Maximum allowable concentration for blending with petroleum jet
fuels (ASTM D7566).
primary: DB-17MS Agilent (30 m × 0.25 mm × 0.25 μm);
secondary: DB-1 MS Agilent (0.8 m × 0.25 mm ×
0.25 μm)
UHP helium, 1.25 mL/min
isothermal 40 °C for 0.2 min, followed by a linear gradient
of 1 °C/min to a temperature 160 °C being held
isothermally for 5 min
6.5 s with 1.06 s hot pulse time
secondary oven: 55 °C; modulator: 15 °C
inlet: 280 °C; FID: 300 °C
dichloromethane (99.9% pure, Acros Organics), 165 s delay
was employed. IR spectra were measured in the region of 4000−650
cm−1 using the spectral resolution of 2 cm−1. Principal component
analysis with singular value decomposition algorithm and mean
centering as a pretreatment technique were carried out using an
Unscrambler X (CAMO Software AS, Norway) on the recorded
spectra.
Physical Properties. Table 4 shows the properties measured in
this study together with the ASTM methods and instruments utilized.
with content of the synthetic component exceeding the maximum
limit required by ATSM D7566 in order to investigate in detail the
effect it had on various properties.
GC × GC. For qualitative analysis of the samples, a twodimensional gas chromatography with time-of-flight and mass
spectrometry detector (GC × GC-TOF/MS) LECO Pegasus GCHRT 4D High Resolution TOF/MS was used. Chromatographic
conditions for GC × GC-TOF/MS are shown in Table 3. The ion
source temperature was set to 250 °C, and the electron energy was 70
eV. Data were collected over an m/z range of 45−550 and were
processed and analyzed via LECO Visual Basic Scripting (VBS)
software, ChromaTOF version 1.90. Identification of the compounds
was achieved by matching the measured mass spectra (match factor
threshold > 800) with Wiley (2011) and NIST (2011) mass spectral
databases. For quantitative analysis of the samples, a two-dimensional
gas chromatography with flame ionization detector (GC × GC-FID)
Agilent 7890B was used. Chromatographic conditions for GC × GCFID are shown in Table 3. Data were collected and processed using
the ChromaTOF software version 4.71 optimized for GC × GC-FID
with a signal-to-noise ratio of 75. Both systems were equipped with a
non-moving quad-jet dual stage thermal modulator and liquid
nitrogen for modulation. For both instruments, 10 μL of sample
was diluted in 1 mL of solvent, and 0.5 μL of the sample solution was
injected with a 20:1 split ratio.
GC × GC-TOF/MS data enabled us to develop a detailed chemical
classification on the GC × GC-FID ChromaTOF. The classification
included carbon numbers between C7 and C20 for all main
hydrocarbon classes, such as n-paraffins, isoparaffins, monocycloparaffins, di- and tricycloparaffins, alkylbenzenes, cycloaromatics (indans,
tetralins, etc.), and alkylnaphthalenes. The weight percent of each
group (all compounds with the same carbon number for the same
hydrocarbon class) were obtained by dividing the peak area of the
group by the total peak area of the sample. Detailed description of the
classification with pictorial representation can be found in previous
papers.17,30,31
Infrared Spectroscopy. All infrared spectra (IR) samples were
recorded using an IRAffinity-1 spectrometer coupled with LabSolution IR software (Shimadzu, Japan). The transmission sampling
technique utilizing a ZnSe sample cell with path length of 0.1053 mm
Table 4. Property Measurements
ASTM
instrument
simulated distillation
(SIM DIST)
density
properties
D2997
viscosity
D7042
freezing point
flash point
hydrogen content
nitrogen content
D2386
D56
D3701
D4629
sulfur content
D5453
gross heat of
combustion
aromatic content
(vol %)
D4809
Trace GC Ultra Gas Chromatograph
(Thermo Scientific)
Stabinger Viscometer SVM 3001
(Anton Paar)
Stabinger Viscometer SVM 3001
(Anton Paar)
K29700 (Koehler Instrument)
Tag 4 Flash Point Tester (Anton Paar)
high-resolution NMR31
Xplorer-NS (Trace Element
Instruments)
Xplorer-NS (Trace Element
Instruments)
6200 Isoperibol Calorimeter (Parr
Instrument Co.)
LC-10 CE (Shimadzu)
D4052
D6379
The experimental investigations were conducted at the wellestablished Fuel Laboratory of Renewable Energy at Purdue
University.
■
RESULTS AND DISCUSSION
Composition of Neat Blending Components. Figure 1
shows the GC × GC-TOF/MS chromatogram of Jet A with all
significant hydrocarbon classes, which were further analyzed
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content of C17 isoparaffins (21.26 wt %). The high amount of
iso-C17 hydrocarbons compared to other isoparaffins can be
explained by the process itself and by the HEFA feedstock.
Camelina consists predominantly of triglycerides containing
linolenic, linoleic, and oleic acids, all with 18 carbons in the
molecule. In HEFA production process, hydrodecarbonylation
and hydrodecarboxylation dominated over hydrodeoxygenation, yielding mainly hydrocarbons with a carbon number one
less than that of fatty acids bonded in molecules of the
feedstock. On the other hand, isoparaffins present in FT-IPK
were in the range of C8 to C15, and their distribution was
normal with a maximum in iso-C12. HEFA and FT-IPK both
contained a small amount of monocycloparaffins in the range
of C8 to C12, and their content did not exceed 3.0 wt %. There
were no detectable dicycloparaffins nor tricycloparaffins in
either of the samples. The total content of aromatics was
extremely low in FT-IPK and HEFA (0.30 and 0.03 wt %
respectively). HEFA contained only alkylbenzenes (C9−C10)
and no cycloaromatics or naphthalenes, while FT-IPK
contained alkylbenzenes (C8−C11), cycloaromatics (C11−
C13), and alkylnaphthalenes (C11).
Further comparison of the SIP and ATJ provided additional
differences as well. n-Paraffins were not detected in either
sample. SIP isoparaffins were in the range of C14 to C16 with
the following concentrations: 0.05 wt % iso-C14, 99.40 wt %
iso-C15 (farnesane), and 0.03 wt % iso-C16. ATJ isoparaffins
were distributed in the range of C8 to C23, where iso-C12 and
iso-C16 content was 82.27 and 11.71 wt %, respectively.
Monocycloparaffins observed in SIP and ATJ were C14 and
C9−C10, respectively. Dicycloparaffins, tricycloparaffins, cycloaromatics, and alkylnaphthalenes were not detected in either
sample. The trace amount of aromatics in SIP came solely from
C15 alkylbenzenes (0.06 wt %). ATJ did not contain any
alkylbenzenes.
Sulfur, Nitrogen, and Hydrogen Content. Table 6
displays the sulfur, nitrogen, and hydrogen contents of neat
blending components. As expected, bio-based blending
components (HEFA, SIP, and ATJ) contained only a
negligible amount of sulfur, while FT-IPK (coal feedstock)
contained an order higher amount of sulfur than that found in
bio-based components. Nitrogen content was slightly higher
for all blending components when compared to Jet A. It was
also obvious that all synthetic blending components had
significantly higher hydrogen content than Jet A fuel. This was
caused primarily by the absence of aromatics, which have a
high carbon/hydrogen ratio. Sulfur and hydrogen contents
were used for net heat of combustion calculations. The values
of the sulfur and hydrogen content in fuel mixtures were
calculated utilizing the constituent component mass fractions
and pertinent individual sulfur and hydrogen contents.
Infrared Spectroscopy. There are basically no methods
for detecting and determining alternative blending components
in petroleum-based Jet A. The method in ref 33, which
measures the content of radiocarbon 14C, can only measure the
content of bio-based alternative blending components;
however, it cannot detect which blending component was
used (e.g., HEFA vs ATJ). Therefore, infrared spectroscopy
was utilized in order to investigate if such a relatively simple
analytical method together with proper chemometric processing can predict which type of alternative blending component
was used in the mixture with Jet A. PCA is one of the most
fundamental chemometric techniques used for the processing
of multivariate data. The aim of the PCA is reduction of the
Figure 1. GC × GC chromatogram of Jet A with section
identifications: (1) n- and isoparaffins, (2) monocycloparaffins, (3)
di- and tricycloparaffins, (4) monoaromatics, (5) cycloaromatics, and
(6) diaromatics.
quantitatively using GC × GC-FID. The hydrocarbon
composition of Jet A and fuel blending components obtained
from GC × GC-FID is shown in Table 5. Further information
on detailed composition of this Jet A sample was discussed
previously.17 Figure 2 shows the GC × GC-TOF/MS
chromatograms of the synthetic blending components
mentioned above. Details on their chemical compositions are
provided in further sections.
FT-IPK was mostly composed of isoparaffins. HEFA was
composed predominantly of n-paraffins and isoparaffins. SIP
and ATJ predominantly contained isoparaffins, while ATJ
contained isoparaffins up to C23. SIP was composed of 99.40
wt % of farnesane (2,6,10-trimethyldodecane) having 15
carbon atoms in its molecule. Farnesane is the only visible
peak with tr′ 4433 s and tr′′ 3.85 s on Figure 2c. The most
abundant constituents of ATJ were two compounds, i.e.,
2,2,4,6,6-pentamethylheptane (tr′ 1332 s and tr′′ 3.55 s) in
concentration of 66.50 wt % and 2,2,4,4,6,8,8-heptamethylnonane (tr′ 3913 s and tr′′ 0.17 s) in concentration of 8.58 wt %.
Two additional C12 isoparaffins were detected in significant
amounts, i.e., 4.63 wt % (tr′ 1712 s and tr′′ 3.65 s) and 4.48 wt
% (tr′ 3729 s and tr′′ 7.2 s). These compounds are clearly
visible in Figure 2d. Aromatic content is limited for all
blending components (ASTM D7566, annexes A1−A5) by the
maximum value of 0.50 wt % and was met by all blending
components.
Further comparison of the HEFA and FT-IPK provided
additional differences. HEFA n-paraffin content was 8.53 wt %
and was distributed in the carbon atom range of n-C8 to n-C17.
On the other hand, FT-IPK contained a very low amount (0.39
wt %) of n-paraffins in the range of n-C10 to n-C16. HEFA
isoparaffins were in the range of C8 to C18, with the highest
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Table 5. Hydrocarbon Type Composition (wt %) of Jet A, FT-IPK, HEFA, SIP, and ATJ
hydrocarbon class
n-paraffins
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
total n-paraffins
isoparaffins
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
total isoparaffins
monocycloparaffins
C7
C8
C9
C10
C11
C12
C13
C14
C15
total
monocycloparaffins
Jet A
0.83
5.05
4.96
3.36
2.37
1.90
1.27
0.76
0.36
0.10
0.02
20.97
FTIPK
0.00
0.00
0.10
0.00
0.13
0.08
0.04
0.03
0.01
0.00
0.00
0.39
HEFA
1.56
2.15
1.38
0.96
0.83
0.65
0.25
0.51
0.13
0.10
0.00
8.53
SIP
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
ATJ
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.28
4.97
6.94
5.36
3.69
3.51
2.63
1.97
0.94
0.23
0.06
0.00
0.00
0.00
0.00
0.00
30.58
0.52
7.93
19.39
23.50
27.70
11.73
5.10
1.07
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
96.94
1.48
11.18
11.35
9.87
8.47
8.17
6.29
5.59
2.35
21.26
3.66
0.00
0.00
0.00
0.00
0.00
89.68
0.00
0.00
0.00
0.00
0.00
0.00
0.05
99.40
0.03
0.00
0.00
0.00
0.00
0.00
0.00
0.00
99.49
0.42
0.25
0.00
0.94
82.27
0.61
0.15
1.30
11.71
1.61
0.00
0.04
0.00
0.03
0.58
0.01
99.93
0.22
3.74
4.47
4.10
2.85
2.25
1.67
0.69
0.12
20.12
0.00
0.06
0.39
0.76
0.83
0.33
0.00
0.00
0.00
2.37
0.00
0.81
0.51
0.29
0.08
0.03
0.00
0.00
0.00
1.73
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.42
0.00
0.42
0.00
0.00
0.01
0.00
0.06
0.00
0.00
0.00
0.00
0.07
hydrocarbon class
Jet A
FTIPK
HEFA
SIP
ATJ
di- and tricycloparaffins
C8
C9
C10
C11
C12
C13
C14
total di- and
tricycloparaffins
total cycloparaffins
0.23
0.78
1.01
1.07
0.80
0.27
0.14
4.30
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
24.41
2.37
1.73
0.42
0.07
alkylbenzenes
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
total alkylbenzenes
0.07
1.79
4.86
3.27
2.15
1.72
1.04
0.35
0.19
0.02
15.46
0.01
0.07
0.08
0.04
0.00
0.00
0.00
0.00
0.00
0.00
0.20
0.00
0.01
0.02
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.03
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.06
0.00
0.00
0.06
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
cycloaromatics
C9
C10
C11
C12
C13
C14
C15
total cycloaromatics
0.14
0.78
1.73
2.24
1.26
0.73
0.01
6.89
0.00
0.00
0.01
0.05
0.01
0.00
0.00
0.07
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.11
0.41
0.64
0.43
0.09
0.01
1.69
0.00
0.02
0.00
0.00
0.00
0.00
0.02
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
24.05
0.30
0.03
0.06
0.00
alkylnaphthalenes
C10
C11
C12
C13
C14
C15
total
alkylnaphthalenes
total aromatics
processing. The selected spectral region of Jet A, FT-IPK,
HEFA, SIP, and ATJ is shown in Figure 3. The selected region
contained sufficient spectral information for the comparison of
the particular jet fuel components36 and contained bands
which can be predominantly attributed to the rocking
vibrations of methyl and methylene groups, skeletal vibrations
of various grouping of carbon atoms, and in-plane and out-ofplane deformations vibrations of bands present in the aromatic
structures. The aromatic bands (805, 767, 741, and 698 cm−1)
can be observed primarily in the spectrum of Jet A. The
absorption intensity of these bands in the spectra of the
blending components with no or low aromatic content is
negligible. The spectrum of ATJ is composed of four dominant
original variables while maintaining as much important
information present in the original data as possible. The
original variables are transformed (using linear combinations)
to usually much lower number of new variables called principal
components (PC). The major output of PCA are two matrices:
scores (each sample has its own set of score values) and
loadings (each original variable has its own set of loadings
values). Projection of the scores and loadings values to the 2D
plots offers interesting insight into the multivariate data. A
more detailed description of PCA can be found elsewhere.34,35
Infrared spectra of the samples were measured in the region
of 4000−650 cm−1; however, only a narrower portion (1320−
680 cm−1) of the recorded spectra was utilized for further
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Figure 2. Comparison of GC × GC-TOF/MS chromatograms of synthetic blending components: (a) FT-IPK, (b) HEFA, (c) SIP, and (d) ATJ.
attributed to the stretching vibration of C−C bond from the
>C(CH3)2 group (1170 cm−1) and the rocking vibration of the
same group (1151 cm−1). The bands that can be attributed to
the CH3 rocking vibrations from groups (R)3−C−CH3 and
(R)3−C−CH2−CH3 can be found at 968 and 919 cm−1,
respectively. The two remaining dominant bands (770 and 735
cm−1) can be attributed to the rocking vibrations of the groups
−CH2− and −(CH2)3−, respectively. The spectrum of HEFA
is mainly composed of the bands mentioned above. The
additional band observed at 723 cm−1 can be attributed to the
rocking vibration of −(CH2)n− for n > 3 and can be associated
with long unbranched hydrocarbon chains. This band was also
observed in Jet A spectrum.
The recorded infrared spectra of Jet A, neat blending
components, and their mixtures were utilized as input data for
the PCA. Although the first three principal components (PC1
to PC3) were able to capture 98% of original data variability, it
was beneficial to use PC4 as well. The plots of PC1 vs PC2,
Table 6. Sulfur (mg/kg), Nitrogen (mg/kg), and Hydrogen
(wt %) Contents in Jet A, FT-IPK, HEFA, SIP, and ATJ
sulfur
nitrogen
hydrogen
Jet A
FT-IPK
HEFA
SIP
ATJ
573
6
13.8
13
9
15.12
2
8
15.45
<1
10
15.33
<1
7
15.47
bands; while the bands at the wavenumbers 1242, 1205, and
926 cm−1 can be attributed to the skeletal vibration of the
group −C(CH3)3, the band at 971 cm−1 can be attributed to
the rocking vibration of group −CH3. The bands observed in
the spectrum of FT-IPK can be attributed to skeletal vibration
of the group −C(CH3)3 (1242 cm−1), the stretching vibration
of C−C bond present in the >C(CH3)2 group (1170 cm−1),
the rocking vibration of the same group (1151 cm−1), and the
rocking vibration of CH3 from (R)3−C−CH2−CH3 grouping.
The spectrum of SIP is also composed of bands, which can be
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Figure 3. IR region of Jet A and neat blending components.
PC1 vs PC3, and PC1 vs PC4 scores can be found in Figure
4a, 4b, and 4c, respectively. The plots of PC1 vs PC2, PC1 vs
PC3, and PC1 vs PC4 loadings are presented in Figure 5a, 5b,
and 5c, respectively. As can be seen in the scores plots, the
position of the points belonging to the neat blending
components can be clearly distinguishable from the positon
of Jet A and more or less from every other neat blending
component. The most significant difference between the point
of Jet A and the points of neat blending components was
observed in the case of ATJ. Moreover, the points of mixtures
of ATJ and Jet A were clearly recognizable and did not overlap
with any other points. The IR spectral features responsible for
the separation of the ATJ/Jet A mixture points and neat ATJ
from neat Jet A were predominantly captured by PC1.
Utilization of both PC1 and PC2 did help to separate the
ATJ/Jet A mixture points from all mixtures composed of the
other blending components (Figure 4a). PC3 and PC4 did not
have significant influence regarding the isolation of ATJ and
ATJ/Jet A mixture points from neat Jet A nor from the other
mixtures. Separation of the other neat blending components
and their mixtures with Jet A from the neat Jet A can be
associated with all four principal components. While PC1 can
be used for mutual separation of neat blending components,
utilization of both PC1 and PC2 offered recognition of the
mixtures (Figure 4a). Nevertheless, the use of only PC1 and
PC2 was not sufficient for separation of mixtures with low
concentrations of FT-IPK, SIP, and HEFA. Even the utilization
of PC3 did not allow us to clearly separate SIP/Jet A mixtures
from low concentrations HEFA/Jet A mixtures. On the other
hand, the utilization of PC3 showed that the distance of FTIPK points to SIP and HEFA points is quite large, so the FTIPK points were clearly isolated (Figure 4b). While the
increasing FT-IPK content in the samples was reflected by
decreasing PC3 score values, an opposite trend was observed
in the case of other blending components. The proper isolation
of SIP and HEFA points was performed utilizing PC4 (Figure
4c). In this case, increasing SIP content in the samples caused
a decrease of PC4 score values. Increasing the blend ratio
resulted in ascending the profile of PC4 score values for the
other mixtures.
While the score plots displayed relationships among the
samples, the loading plots (Figure 5) show the influence of the
particular original variables (wavenumbers) on the score plots
and relationship among the original variables. The loading
plots were used to additionally interpret the score plots
discussed above. Although all wavenumbers have their loadings
values, only selected ones were presented in the loading plots.
Only the wavenumbers, which can be attributed to the highest
point of the chosen intensive absorption bands, were selected
for the purpose of the PCA loadings presentation. The selected
wavenumbers correspond to the wavenumbers commented
during the infrared spectra interpretation. All aromatic bands
(805, 767, 741, and 698 cm−1) can be found in the right
bottom quadrant of all three loading plots. The influence of the
aromatic band loadings can be associated with the position of
the Jet A point in all score plots as this point was also located
in the right bottom quadrant. Since the increasing ratio of the
blending components in the mixtures with Jet A was always
accompanied by the decrease of the aromatics content, the
general direction of the mixture score point movements can be
observed in the left top quadrant. The position of ATJ points
in the score plots was strongly influenced by wavenumbers
1242 and 1205 cm−1. At these wavelengths PC1 loading values
were negative; hence, increasing the ATJ content in the
samples was reflected by decreasing PC1 score values of ATJ
mixtures. The effect of additional ATJ bands (represented by
wavenumbers 971 and 926 cm−1) on PCA score plots was
lower. The position of the neat FT-IPK in Figure 4b (left
bottom quadrant) can be associated with the negative value of
the PC3 loading of wavenumber 1123 cm−1, which is related to
the absorption band in the spectrum of FT-IPK. On the other
hand, the localization of the SIP and HEFA sample points in
the upper half of the score plot in Figure 4b can be associated
with positive values of PC3 loadings of wavenumbers 735 and
723 cm−1, which are related to the bands present in the spectra
of SIP and HEFA, respectively. The opposite effect of the
mentioned wavenumbers was potentially responsible for the
isolation of the FT-IPK samples. A similar situation was
observed in Figure 4c and Figure 5c. Negative values of PC4
loadings of wavenumbers 1123 and 735 cm−1 (Figure 5c) can
be associated with decreasing PC4 score values of the mixtures
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Figure 5. PCA loadings plots of PC1 vs PC2 (a), PC1 vs PC3 (b),
and PC1 vs PC4 (c) of the selected wavenumbers.
Figure 4. PCA score plots of PC1 vs PC2 (a), PC1 vs PC3 (b), and
PC1 vs PC4 (c) of neat jet fuel components (×) and mixtures of
blending components with Jet A (○).
(Figure 5c) can be attributed to increasing PC4 score values of
HEFA mixtures (Figure 4c). This opposite influence of
wavenumbers was observed as the absorption bands of SIP
with increasing SIP content (Figure 4c). On the other hand,
the positive PC4 loading value of wavenumber 723 cm−1
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Table 7. Hydrocarbon Type Composition (wt %) of FT-IPK, HEFA, SIP, and ATJ with Jet A Mixtures
paraffins
FT 10
FT 20
FT 30
FT 40
FT 50
FT 60
HEFA 10
HEFA 20
HEFA 30
HEFA 40
HEFA 50
HEFA 60
SIP 5
SIP 10
SIP 15
ATJ 10
ATJ 20
ATJ 30
ATJ 40
ATJ 50
ATJ 60
cycloparaffins
aromatics
n-
iso-
mono-
di- and tri-
alkylbenzenes
cyclo-
alkylnaphthalenes
19.0
17.0
15.0
13.0
11.0
8.9
19.8
18.6
17.4
16.2
14.9
13.7
20.0
19.0
17.9
19.0
17.0
14.9
12.9
10.8
8.7
36.9
43.2
49.7
56.2
62.8
69.5
36.2
41.9
47.6
53.4
59.3
65.2
33.9
37.2
40.5
37.2
43.8
50.5
57.3
64.2
71.2
18.4
16.7
15.0
13.3
11.5
9.7
18.4
16.6
14.8
13.0
11.2
9.3
19.2
17.3
18.2
18.2
16.3
14.4
12.4
10.4
8.4
3.9
3.5
3.1
2.6
2.2
1.8
3.9
3.5
3.1
2.6
2.2
1.8
4.1
3.9
3.7
3.9
3.5
3.1
2.6
2.2
1.8
14.0
12.5
11.1
9.6
8.1
6.5
14.0
12.5
11.0
9.5
8.0
6.4
14.7
14.0
12.2
14.0
12.5
11.0
9.5
8.0
6.4
6.2
5.6
4.9
4.3
3.6
2.9
6.2
5.6
4.9
4.2
3.5
2.9
6.6
6.2
5.9
6.2
5.6
4.9
4.2
3.5
2.9
1.5
1.4
1.2
1.0
0.9
0.7
1.5
1.4
1.2
1.0
0.9
0.7
1.6
1.6
1.4
1.5
1.4
1.2
1.0
0.9
0.7
Figure 6. Simulated distillation profiles of Jet A, FT-IPK, HEFA, SIP, and ATJ.
chemical content of the fuel, especially of Jet A, where huge
differences can be expected. Further steps regarding the
utilization of FTIR and PCA for this topic should also focus on
evaluation of the components.
Composition of Fuel Blends. The simplified mixture
composition (Table 7) was calculated utilizing the constituent
component mass fractions and pertinent individual composition values. A set of ten samples was randomly chosen and
and HEFA were responsible for the clear isolation of SIP
points in Figure 5c.
To conclude, utilization of these score plots enabled a simple
identification of the samples while yielding clusters formation.
Even the mixtures with the lowest blending component
content were distinguishable from Jet A and other mixtures
that can be utilized for some classification purposes. Nevertheless, a possible obstacle would be related to the specific
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Figure 7. Differences between predicted and measured SIM DIST values for FT-IPK mixtures.
measured via GC × GC-FID for validation of these
calculations. The measured and the calculated data were in
good agreement (Table S1 in the Supporting Information).
GC × GC-TOF/MS chromatograms of the mixtures with the
maximum concentration of the synthetic blending component
in Jet A are displayed in Figure S7 in the Supporting
Information.
Distillation Profile. The D7566 standard requires the
physical distillation data (D86) to be reported. In addition to
this, D7566 allows the use of the SIM DIST (D2887) method;
however, the data should be converted to estimated D86 data.
Due to the fact that the conversion equation was developed
using petroleum-based jet and diesel fuels,37 this conversion is
not approved by D7566 for neat alternative fuel blending
components, but just for the final blends with Jet A/A-1.
Results from SIM DIST (D2887) runs are shown in Figure 6.
These results were also converted to the estimated D86 results
and are shown in Figure S1 in the Supporting Information.
Estimation of D86 results from D2887 did not yield reliable
results for neat ATJ and SIP, which demonstrates the reason
D86 data from SIM DIST are not approved as a method per
ASTM D7566 for any alternative fuel blending components. In
this study, HEFA demonstrated the widest distillation range
between 5 and 95 wt % recovered. HEFA also displayed the
highest final boiling point (FBP) while still having the lowest
initial boiling point (IBP). At the same time, the HEFA
distillation range was the most similar to that of standard Jet A
fuel although HEFA and Jet A carbon number distributions
showed discrepancies. The difference in the HEFA distillation
profile was caused mostly by the high content of C17
hydrocarbons that made the distillation curve more skewed
in nature. FT-IPK showed a very normal carbon number
distribution, similar to that of Jet A; however, its distillation
range was narrower. Very simple composition of SIP (basically
the only one hydrocarbon, 2,6,10-trimethyldodecane) yielded
the narrowest distillation range. SIM DIST data of farnesane
(Figure 7) were in excellent agreement with its boiling point
(251.23 ± 12.16 °C at 760 mm/Hg based on Knovel).
Similarly, the high concentration of 2,2,4,6,6-pentamethylheptane in ATJ caused the very narrow distillation range from 0 to
70 wt %.
SIM DIST data of each sample were obtained via GC-FID
following the D2887 method; a detailed description can be
found in a previous work.38 Additionally, SIM DIST data of
each binary mixture (e.g., FT 10, SIP 20, etc.) were also
calculated from the data of the neat components (e.g., Jet A
and FT-IPK, Jet A and SIP, etc.). These calculations were
carried out utilizing ChromCard software (standard software
for GC control and data processing). In the first step,
chromatograms of two neat blending components were
multiplied by the mass fraction of each component. In the
second step, these two rescaled chromatograms of neat
blending components were summed. This resultant chromatogram was further processed as a chromatogram of the blend
with specific composition. For validation purposes, the results
calculated were compared to those obtained by direct
measurements. Differences between predicted and measured
SIM DIST values for FT-IPK mixtures are displayed in Figure
7. HEFA, SIP, and ATJ results can be found in Figures S2, S3,
and S4, respectively, in the Supporting Information. Additionally, the differences were compared to repeatability and
reproducibility of ASTM D2887.37 Every data point felt within
the reproducibility of D2887. However, not every data point
felt within the repeatability of D2887. The prediction could be
improved by optimizing of GC method for jet fuels by
decreasing the temperature ramp rate. In these experiments, a
temperature ramp rate of 15 °C/min was used in order to also
measure samples with a wide distillation range in an optimal
time. In the method we used, a 0.10 min difference in retention
time corresponded to a 2.5 °C difference in boiling point.
Since ATJ and SIP samples contained only a few compounds,
their peaks were relatively broad and even a small shift of the
retention time would have a significant effect on the boiling
point. The lower temperature ramp rate was not tested here as
the SIM DIST data calculated here predicted better flash point
values when compared to those obtained experimentally.
Further discussion is provided in the Flash Point section. In
our previous paper,17 we did not test this method; therefore,
this method was also tested on HEFA produced from tallow
and mixed fat, and the results can be found in the Supporting
Information.
Density. Each blending component had a lower density
than the minimum limit required by ASTM D7566 (0.775−
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Table 8. Density at 15 °C (g/cm3) for Jet A, FT-IPK, HEFA, SIP, ATJ, and Their Mixtures
D4052
eq 1
eq from ref 31
D4052
eq 1
eq from ref 31
D4052
eq 1
eq from ref 31
D4052
eq 1
eq from ref 31
FT 10
FT 20
FT 30
FT 40
FT 50
FT 60
FT-IPK
0.8010
0.8011
0.8013
HEFA 10
0.7966
0.7965
0.7968
HEFA 20
0.7920
0.7919
0.7924
HEFA 30
0.7874
0.7873
0.7878
HEFA 40
0.7828
0.7827
0.7819
HEFA 50
0.7782
0.7781
0.7786
HEFA 60
0.7597
−
0.7594
HEFA
0.7874
0.7873
0.7889
0.7828
0.7827
0.7846
0.7783
0.7781
0.7802
0.7598
−
0.7622
0.8012
0.8011
0.8015
SIP 5
0.7966
0.7965
0.7974
SIP 10
0.7922
0.7919
0.7931
SIP 15
0.8040
0.8040
0.8040
ATJ 10
0.8022
0.8023
0.8024
ATJ 20
0.8007
0.8006
0.8008
ATJ 30
ATJ 40
ATJ 50
ATJ 60
ATJ
0.8011
0.8010
0.8013
0.7965
0.7964
0.7969
0.7919
0.7918
0.7925
0.7874
0.7872
0.7880
0.7831
0.7826
0.7835
0.7780
0.7780
0.7789
0.7596
−
0.7599
SIP
Jet A
0.7720
−
0.7718
0.8057
−
0.8057
0.840 g/cm3). This can be attributed to the lack of aromatic
compounds in these components (Table 6). Therefore,
addition of blending components to Jet A lowered the final
density. When comparing the neat blending components
(Table 8), we saw that the density increased in the following
order: ATJ < FT-IPK < HEFA < SIP. Density values of FTIPK, HEFA, and ATJ were in close proximity (the difference
was on the fourth decimal number). Similarly, density values of
equal volumetric concentrations of each blending component
in Jet A followed the same order.
Our measurements showed that the mixture volumes were
all additive; hence, the relationship between the mixture
density and the blending component concentration was linear.
This enabled calculating the density of all mixtures via the
simple eq 1.
ρm =
∑ νρi i
i
(1)
where ρm is the density of the mixture, vi is the volume fraction
of the neat blend component, and ρi is the density of neat
blend component. Prediction of density values at 15 °C from
GC × GC-FID chemical composition was described
previously31 with the procedure of how the distribution of
each carbon number in each hydrocarbon class can influence
the total density value. Table 8 shows the results of all samples
in this study measured via D4052 and the results calculated
from two methods, i.e., eq 1 and from GC × GC-FID data
utilizing the method from a previous study.31 Both equations
produced very similar results.
Viscosity. Viscosity values at −20 °C of the neat blending
components increased in the following order: FT-IPK < HEFA
< ATJ < SIP. Results in this study showed that there is a
second degree (quadratic) polynomial relationship between
viscosity and the blending component concentration. Therefore, when the viscosity of the neat blending components is
higher than that of Jet A, the curve opens upward (the case for
HEFA, SIP, and ATJ) and when the viscosity of the neat
blending components is lower than that of Jet A, the curve
opens downward (the case for FT-IPK). Figure 8 displays the
results of viscosity values of all the mixtures prepared. All
mixtures met the maximum limit of 8 mm2/s according to
ASTM D7566.
Figure 8. Comparison of kinematic viscosity at −20 °C for all
prepared samples with a magnified portion of HEFA and ATJ blends
with concentrations above 90 vol %.
SIP viscosity (13.72 mm2/s) was much higher than that of
FT-IPK (3.44 mm2/s), HEFA (5.20 mm2/s), and ATJ (5.23
mm2/s). Density values of FT-IPK, HEFA, and ATJ were
similar; however, the viscosity of FT-IPK was lower (by
∼30%) than that of HEFA and ATJ. One significant
phenomenon was observed for the viscosity trend of the
mixtures. Despite the fact that HEFA viscosity was lower than
that of ATJ, the viscosity values of the mixtures did not follow
this order. HEFA mixture viscosities were slightly higher than
that of ATJ for all mixtures up to 95 vol %. This trend was
reversed for the mixtures above 95 vol %, which can be
observed on the magnified portion of Figure 8. The similar
viscosity of ATJ and HEFA can be explained as ATJ
(composed of C12 and C14 isoparaffins in 94.62 wt %) which
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Table 9. Freezing Point of Jet A, FT-IPK, HEFA, SIP, ATJ, and Their Mixtures (°C)
D2386
D2386
D2386
D2386
FT 10
FT 20
FT 30
−54.0
HEFA 10
−54.0
HEFA 20
−54.5
HEFA 30
FT 40
FT 50
FT 60
FT-IPK
−55.0
HEFA 40
−59.0
HEFA 50
−60.0
HEFA 60
< −70.0
HEFA
−52.0
−53.0
−51.0
SIP 5
−51.5
SIP 10
−52.0
SIP 15
−53.5
−52.0
ATJ 10
−53.0
ATJ 20
−53.0
ATJ 30
ATJ 40
ATJ 50
ATJ 60
ATJ
−52.5
−52.5
−52.5
−54.0
−57.5
−60.0
< −70.0
SIP
−55.0
Jet A
< −70.0
−51.0
Table 10. Flash Points (°C) of Jet A, FT-IPK, HEFA, SIP, ATJ, and Their Mixtures Determined Using ASTM D56 and
Calculated from ASTM D7215 and eq 2
FT 10
D56
D7215
eq 2
D7215a
eq 2a
D56
D7215
eq 2
D7215a
eq 2a
D56
D7215
eq 2
D7215a
eq 2a
D56
D7215
eq 2
D7215a
eq 2a
42.5
40.9
42.3
42.0
43.0
HEFA 10
FT 20
42.5
40.8
42.2
41.5
42.8
HEFA 20
43.5
42.1
43.3
42.0
43.1
SIP 5
42.5
42.0
43.2
41.4
42.6
SIP 10
45.0
41.6
42.9
42.5
43.5
ATJ 10
45.5
42.1
43.2
42.9
43.7
ATJ 20
42.0
41.7
43.0
42.8
43.7
43.0
43.0
43.9
43.5
44.2
FT 30
42.5
40.3
41.9
41.1
42.5
HEFA 30
41.5
41.6
42.9
40.7
42.1
SIP 15
44.5
42.2
43.4
43.2
44.0
ATJ 30
44.0
43.8
44.5
44.7
45.1
FT 40
FT 50
41.5
40.0
41.7
40.8
42.2
HEFA 40
41.5
40.1
41.8
40.4
42.0
HEFA 50
42.0
40.0
41.7
40.2
41.8
HEFA 60
41.5
40.2
42.4
−
−
HEFA
41.0
41.2
42.6
39.9
41.5
41.0
41.0
42.5
39.7
41.3
42.5
40.6
42.3
39.4
41.1
42.5
39.7
41.8
−
−
SIP
>110
−b
−b
−
−
ATJ 40
46.0
45.2
45.6
46.3
46.5
FT 60
FT-IPK
Jet A
43.0
−
−
−
−
ATJ 50
ATJ 60
ATJ
46.0
47.6
48.8
48.3
48.1
46.0
50.1
50.6
50.4
49.5
48.5
55.4
52.6
−
−
a
Predicted data from SIM DIST. bNot calculated due to the D56 method limitations.
several researchers.17,23,40 In this study, SIP, ATJ, and FT-IPK
freezing point values were below the detection limit (less than
−70 °C) of the D2386 apparatus due to the fact that SIP and
ATJ did not contain any n-paraffins and FT-IPK contained
only a negligible amount (0.39 wt %). On the other hand,
HEFA contained a significant amount of n-paraffins (8.53 wt
%), which caused the freezing point value to be −55 °C.
The freezing point values of the mixtures were observed to
fall in between the freezing points of their blending
components (Table 9). The repeatability of freezing point
values in this study was 0.5 °C; the repeatability of the D2386
method is reported as 1.5 °C, which could be the reason why
several mixtures had the same freezing point. The maximum
freezing point values permitted by ASTM are −40 and −47 °C
for Jet A and Jet A-1, respectively. Therefore, the addition of
these blending components to Jet A/A-1 does not increase this
value. However, it was shown in previous paper17 that the final
freezing point can be increased if the batch of HEFA used for
mixing has a freezing point higher than that of Jet A. As already
discussed in a previous paper,17 none of the Cookson
equations for freezing point predicted accurate results for
HEFA/Jet A mixtures. Similarly, none of the Cookson
acted as a surrogate mixture for HEFA (composed of n-, iso-,
and monocycloparaffins).
In spite of the fact that both SIP and ATJ samples were
composed mostly of isoparaffins, there was a significant
difference between their viscosity values. The high viscosity
value of SIP stemmed from the viscosity of its most prominent
compound, i.e., farnesane (99.4 wt %). The carbon number of
the most abundant component of ATJ (66.50 wt % of
2,2,4,6,6-pentamethylheptane) was 3 times lower than that of
farnesane and the level of branching was higher, both of which
resulted in a lower ATJ viscosity value. As for FT-IPK and
HEFA samples, their isoparaffins content was in close
proximity. HEFA contained more n-paraffins than FT-IPK. nParaffins have higher viscosity values than those of isoparaffins
for the same carbon number. Moreover, FT-IPK contained
isoparaffins with a lower carbon number than HEFA.
Freezing Point. The freezing point is very dependent on
the molecular structure.17 n-Paraffins exhibit the highest
freezing point among all hydrocarbon groups,39 and the
freezing point increases with increasing carbon number.
Therefore, the freezing point is driven by the heaviest nparaffins in the fuel. This observation was also confirmed by
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Article
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Table 11. Net Heat of Combustion (MJ/kg) of Jet A, FT-IPK, HEFA, SIP, ATJ, and Their Mixtures with Jet A Determined
Using ASTM D4809 and Calculated from eq 3 and ASTM D3338
FT 10
D4809
eq 3
D3338
D4809
eq 3
D3338
43.11
43.19
43.19
HEFA 10
FT 20
FT 30
FT 40
FT 50
FT 60
43.19
43.28
43.26
HEFA 20
43.32
43.37
43.34
HEFA 30
43.54
43.45
43.42
HEFA 40
43.57
43.54
43.51
HEFA 50
43.67
43.63
43.60
HEFA 60
44.00
−
43.96
HEFA
43.35
43.51
43.53
43.55
43.61
43.63
43.64
43.72
43.73
44.15
−
44.13
43.16
43.21
43.24
SIP 5
43.27
43.31
43.34
SIP 10
43.35
43.41
43.43
SIP 15
D4809
eq 3
D3338
43.13
43.15
43.15
ATJ 10
43.13
43.20
43.20
ATJ 20
43.22
43.24
43.24
ATJ 30
D4809
eq 3
D3338
43.24
43.20
43.19
43.34
43.29
43.27
43.34
43.38
43.36
SIP
FT-IPK
Jet A
44.01
−
44.08
ATJ 40
43.11
−
43.13
43.42
43.48
43.44
ATJ 50
ATJ 60
ATJ
43.53
43.57
43.54
43.63
43.67
43.64
44.06
−
44.00
mixtures containing other blending components. Results from
eq 2 and the original equation from ASTM method D7215 are
shown in Table 10. Additionally, both equations were used for
prediction of the flash point from SIM DIST data calculated
from the data of neat components (discussed in the Distillation
Profile section). Most of the predicted values from both
equations were within the repeatability of the ASTM D56
method (1.2 °C) except for three samples (SIP 5, SIP 10, and
ATJ). The values highlighted in Table 10 are those where the
D7215 equation predicted better results than eq 2.
Net Heat of Combustion. Net heat of combustion
(NHC) values of all neat blending component samples were
higher than the minimum limit of 42.8 MJ/kg defined by
ASTM D1655. NHC decreases in the order of paraffins >
cycloparaffins > aromatics. NHC of isoparaffins is in most
cases slightly lower than that of n-paraffins for the same carbon
number.29,39 When the neat blending components (Table 10)
were compared, NHC increased in the following order: FTIPK < SIP < ATJ < HEFA. All samples exhibited higher NHC
values than that of Jet A; therefore, the mixing did not
negatively influence the final NHC value.
The same approach that was utilized for density was used for
NHC in order to discover how the NHC was affected by the
chemical composition. This approach enables us to compare
the contribution to the total NHC of each carbon number and
each hydrocarbon class. The net heat of combustion
calculation from GC × GC-FID chemical compositions was
previously introduced in the literature29 and was further
detailed elsewhere.17 NHC data calculated from GC × GCFID can be found in the Supporting Information (Table S3).
Additionally, NHC values of each mixture can be simply
calculated from the Jet A and blending component NHC
values, as displayed in eq 3.
equations predicted the accurate results for the other blending
components utilized in this study. The data calculated from the
Cookson equations can be found in the Supporting
Information.
Flash Point. The flash point of the neat blending
components increased in the following order: FT-IPK <
HEFA < ATJ < SIP. The SIP flash point could not be
measured as the D56 method range is only up to 110 °C. This
observation was supported also by the IBP values of these
samples. Flash point values of pure hydrocarbons increase with
increasing carbon number39 and also as expected increase with
increasing boiling point. Based on the findings in our previous
work,17 isoparaffins had the lowest flash point among all of the
saturated hydrocarbons with the same carbon number. FT-IPK
and HEFA flash point values were very similar (the difference
was only 1 °C); however, the FT-IPK flash point was lower
than that of HEFA even though the content of isoparaffins
with low carbon numbers (C8 and C9) was higher in HEFA.
FT-IPK contained, in addition to HEFA, 0.30 wt % of
aromatics (up to C13). These aromatics have a low flash point
and potentially could lower the final flash point.
Similar to the freezing point, the flash point values of all the
mixtures prepared fell between the values of the neat blend
components (e.g., Jet A flash point was 43.0 °C, ATJ flash
point was 48.5 °C; therefore, all Jet A/ATJ mixtures flash point
values were between 43.0 and 48.5 °C). Due to this, the
components with flash point values lower (FT-IPK and
HEFA) than that of Jet A decreased the final flash point of
each mixture. On the contrary, the components with flash
point values higher (SIP and ATJ) than that of Jet A increased
the final flash point of each mixture. The repeatability of the
ASTM D56 method is 1.2 °C, which could explain the reason
of several mixtures with the same flash point value.
In our previous paper,17 a new equation for calculation of
HEFA/Jet A mixtures flash point was developed:
NHCm =
∑ wi NHCi
i
CFPD56 = − 39.244 + 0.246TIBP − 0.058T5% + 0.428T10%
(2)
(3)
where NHCm is the net heat of combustion of the mixture, wi
the weight fraction of the neat blend component, and NHCi
the net heat of combustion of the neat blend component.
Another method that can be used for NHC calculations for jet
fuels utilizes distillation data, aromatic content (vol %), and
density is the ASTM method D3338. Although, this method
In this equation, CFP is the calculated flash point, TIBP the
initial boiling point temperature, and T5% and T10% the
temperatures at which 5 and 10 wt % of the sample were
recovered, respectively. TIBT, T5%, and T10% are data from
simulated distillation. Here, this equation was tested for
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Energy & Fuels
■
was not originally designed for alternative aviation fuels, results
from our previous work17 showed that this method was very
suitable for HEFA/Jet A mixtures. Here, eq 3 and the D3338
method were also tested for other alternative blending
components. The results obtained in this study were compared
to experimental data obtained via ASTM D4809. The
difference was below the reproducibility and the repeatability
of ASTM D4809. Therefore, further improvement of the
equation from ASTM D3338 was not necessary. Comparison
of all results obtained from ASTM D4809, D3338, and eq 3 are
shown in Table 11.
■
Article
ASSOCIATED CONTENT
S Supporting Information
*
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.energyfuels.9b00105.
Distillation profiles of Jet A, FT-IPK, HEFA, SIP, and
ATJ estimated from SIM DIST data; difference between
predicted and measured SIM DIST values for HEFA
mixtures; difference between predicted and measured
SIM DIST values for SIP mixtures; difference between
predicted and measured SIM DIST values for ATJ
mixtures; difference between predicted and measured
SIM DIST values for HEFA produced from tallow;
difference between predicted and measured SIM DIST
values for HEFA produced from mix fat; comparison of
GC × GC-TOF/MS chromatograms of fuel blending
component and Jet A mixtures; hydrocarbon type
composition (wt %) for ten selected samples; freezing
point of Jet A, FT-IPK, HEFA, SIP, ATJ, and their
mixtures (°C) calculated from Cookson equations; and
net heat of combustion contribution (MJ/kg) for every
carbon number from each hydrocarbon class (PDF)
SUMMARY AND CONCLUSION
In this study, detailed compositions of Jet A and four
alternative blending components, i.e., FT-IPK, HEFA (from
camelina), SIP, and ATJ, were achieved using comprehensive
two-dimensional gas chromatography with electron ionization
high-resolution time-of-flight and mass spectrometry and flame
ionization detectors. Each blending component had a specific
chemical composition and an individual number of compounds. Infrared spectroscopy and principal components
analysis were utilized as supplementary techniques in order
to clearly demonstrate the differences among the blending
components and Jet A. Mixtures of Jet A and each blending
component were prepared in varying ratios. Main physiochemical properties of all blending components and all
mixtures were determined. A method for calculating the
simulated distillation data of the mixtures was introduced and
validated. Density and net heat of combustion of the mixtures
were additive and were simply calculated from Jet A and HEFA
neat values. Viscosity was not additive. The correlation
between the viscosity and increasing concentrations of the
blending components in Jet A displayed a second-degree
polynomial trend. Slight inconsistency in viscosity was
observed for HEFA and ATJ mixtures. The freezing point of
blending components was lower than that of Jet A; therefore,
the final freezing point was not negatively affected. Zero or
negligible amount of n-paraffins in FT-IPK, ATJ, and SIP
prevented the detection of the freezing point via ASTM
D2386. The freezing point of all mixtures fell between freezing
points of individual blend components and no inconsistencies
were observed. Similarly, the flash point of all mixtures fell
between flash points of individual blend components. The
components with a lower flash point value (FT-IPK and
HEFA) than that of Jet A decreased the final flash point of
each mixture. On the contrary, the components with higher
flash point values (SIP and ATJ) than that of Jet A increased
the final flash point of each mixture. An equation for flash
point calculations, which was introduced in our previous paper,
was further validated in this study. Calculated simulated
distillation data yielded similar flash point values from this
equation when compared to flash point values obtained using
experimentally measured simulated distillation data. The net
heat of combustion (NHC) of each blending component was
higher than that of Jet A; therefore, the mixing did not
negatively influence the final NHC value. The ASTM D3338
for the calculation of NHC was validated, and it was shown
that this method produced very similar results to those
experimentally obtained from the ASTM D4809.
■
AUTHOR INFORMATION
Corresponding Author
*E-mail: gkilaz@purdue.edu. Tel.: 765-494-7486. Fax: 765494-6219.
ORCID
Petr Vozka: 0000-0002-8984-9398
Gozdem Kilaz: 0000-0002-0302-6527
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
This work was supported by the U.S. Navy, Office of Naval
Research (N000141613109 awarded by the Naval Enterprise
Partnership Teaming with Universities for National Excellence
(NEPTUNE) Center for Power and Energy Research). This
work was also supported by the National Program of
Sustainability (NPU I LO1613, MSMT-43760/2015). The
authors thank Dr. James T. Edwards (USAF) for providing the
fuel samples and for his contribution to the Introduction
section.
■
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