sustainability
Article
Strategies to Introduce n-Butanol in Gasoline Blends
Magín Lapuerta *, Rosario Ballesteros and Javier Barba
Escuela Técnica Superior de Ingenieros Industriales, University of Castilla-La Mancha, Av. Camilo José Cela s/n,
13071 Ciudad Real, Spain; [email protected] (R.B.); [email protected] (J.B.)
* Correspondence: [email protected]
Academic Editors: Gilles Lefebvre and Francisco J. Sáez-Martínez
Received: 13 February 2017; Accepted: 7 April 2017; Published: 12 April 2017
Abstract: The use of oxygenated fuels in spark ignition engines (SIEs) has gained increasing attention
in the last few years, especially when coming from renewable sources, due to the shortage of fossil
fuels and global warming concern. Currently, the main substitute of gasoline is ethanol, which helps
to reduce CO and HC emissions but presents a series of drawbacks such as a low heating value
and a high hygroscopic tendency, which cause higher fuel consumption and corrosion problems,
respectively. This paper shows the most relevant properties when replacing ethanol by renewable
n-butanol, which presents a higher heating value and a lower hygroscopic tendency compared to the
former. The test matrix carried out for this experimental study includes, on the one hand, ethanol
substitution by n-butanol in commercial blends and, on the other hand, either ethanol or gasoline
substitution by n-butanol in E85 blends (85% ethanol-15% gasoline by volume). The results show that
the substitution of n-butanol by ethanol presents a series of benefits such as a higher heating value and
a greater interchangeability with gasoline compared to ethanol, which makes n-butanol a promising
fuel for SIEs in commercial blends. However, the use of n-butanol in E85 blends substituting either
gasoline or ethanol may cause cold-start problems due to the lower vapor pressure of n-butanol. For
this reason, a combined substitution of n-butanol by both gasoline and ethanol is proposed so that
n-butanol can be used without start problems.
Keywords: n-butanol; gasoline; E85; interchangeability; density; heating value; vapor pressure
1. Introduction
The gradual depletion of fossil fuels along with concern about global warming have led to the use
of biofuels in internal combustion engines (ICEs) [1] Among various biofuels, bio-alcohols have been
investigated as alternative engine fuels because of their potential for improving engine performance
and reducing pollutant emissions [2]. Bio-alcohols such as ethanol and butanol can reduce the life-cycle
greenhouse emissions, due to their biological production processes. In fact, ethanol is normally used
in spark ignition engines (SIEs) replacing gasoline [3–6]. Both of the aforementioned alcohols have
also been used in compression ignition engine (CIEs) as a diesel partial substitute [7–10].
This paper focuses on the use of alcohols in SIEs, in which the most used bio-alcohol is ethanol,
which is very common in many countries. The main advantage of this fuel is the reduction of CO
and HC emissions when used in SIEs as a gasoline substitute [5,11]. Particularly, ethanol has been
proved to reduce the extra emissions of CO and HC during cold-start conditions with respect to hot
engine conditions [4]. In direct-injection SIEs, which have been gaining prominence in the last few
years, ethanol has been shown to reduce NOx emissions slightly [3] and PM emissions considerably [6].
The lower heating value of ethanol is much lower than that of gasoline fuel, which causes higher fuel
consumption. However, the thermal brake efficiency has been shown to slightly increase [12]. Ethanol
could also present corrosion problems in the injection system due to its hydroscopic tendency. Ethanol
also presents low lubricity [13], which can cause problems in gasoline direct-injection engines. Finally,
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according to Rodríguez-Antón et al. [14], the addition of ethanol increases the vapor pressure of the
blend only up to 35% by volume. A higher ethanol content would reduce the vapor pressure that leads
to start problems [4].
n-butanol is considered the most promising bio-alcohol because of its numerous advantages over
short-chain alcohols (methanol and ethanol mainly), including a higher energy density (higher lower
heating values and higher density), lower viscosity, and higher lubricity. Additionally, n-butanol is
much less hygroscopic and corrosive than ethanol. Besides, n-butanol seems to have a very interesting
potential because its properties are very similar to those of gasoline; therefore, it would be compatible
with the current fuel distribution infrastructure. n-butanol is a second-generation biofuel since it
can be produced from lignocellulosic or waste biomass, with lower lifecycle greenhouse emissions
than ethanol [15]. Currently, it can be produced through either an acetone–n-butanol–ethanol (ABE)
fermentation process or an isopropanol–n-butanol–ethanol (IBE) fermentation process [16].
However, n-butanol has lower vapor pressure compared to ethanol and obviously compared to
gasoline, which is a very evaporative fuel. This drawback could cause cold-start problems in SIEs
when n-butanol is used in high proportions.
Some authors [3,17–19] have reported studies using gasoline-butanol blends in SIEs.
Costagliola et al. [17] tested 10% n-butanol (as well as different ethanol contents) in a port-fuel injection
(PFI) engine showing similar benefits in CO, HC, and PM emissions as with ethanol, but also similar
increases in carbonyl emissions. Galloni et al. [18] tested gasoline and n-butanol (20% and 40% butanol
mass percentage) also in PFI engine. When using a B40 blend, power delivered at same engine speed
decreased about 13%, mainly due to the difference between heating values. HC and NOx emissions
decreased slightly, whereas CO emissions did not suffer any significant change when using B40.
Again in a PFI engine, Li et al. [19] also observed lower CO (4.2%), HC (18.9%), and NOx (5.5%)
emissions when using B30 compared to gasoline as a baseline fuel keeping the engine load constant at
300 kPa of the brake mean effective pressure. Fournier et al. [3] tested gasoline blended with butanol,
butanol–ethanol, and butanol–ethanol-acetone, with butanol contents up to 40% in volume, in both
direct and port-fuel injection (PFI), showing that benefits in HC emissions in PFI engines turned into
HC increases in direct-injection engines.
In this study, ethanol is replaced by n-butanol in commercial ethanol–gasoline blends, as well as
in E85 blends (85% ethanol-15% gasoline by volume). Some properties of the blends were measured in
order to compare the use of n-butanol instead of ethanol in commercial blends for their use in SIEs.
The values of the different properties measured must be within the limits considered in EN 228 and EN
15376 standards. In summary, this paper discusses the advantages and drawbacks of using n-butanol
instead of ethanol in different percentages and blends considering current European regulations. Vapor
pressure, limited in both the E85 standard (CEN/TS 15293) and the gasoline standard (EN 228) was
revealed as the most restrictive property. Within this European legal framework, the use of oxygenated
compounds such as methanol, ethanol, isopropyl, ter-butyl, isobutyl alcohols, and ethers (with five or
more carbon atoms) is explicitly considered. However, n-butanol should be included within the group
of “other oxygenated compounds” despite having a similar octane number than gasoline, and closer
polarity to that of gasoline, and thus greater miscibility than ethanol.
2. Experimental Procedure and Fuels
The whole test matrix (shown in Figure 1) carried out in this experimental study is divided into
three submatrices (red, blue, and green dots) in order to study the most appropriate strategy for the
use of n-butanol in commercial blends. First, commercial gasoline–ethanol blends in which ethanol
(up to 10% by volume) was replaced by n-butanol (up to 16% by volume) were studied, keeping the
oxygen content (limited by 3.7% by mass) constant, as limited by the EN 228 standard. Moreover,
similar tests were carried out limiting the oxygen content to 6 and 7.4% by mass, considering possible
future regulations. This submatrix is marked with red dots in Figure 1. Second, considering E85 as a
baseline fuel (marked in yellow), ethanol was replaced by n-butanol up to 50% by volume of ethanol
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baseline fuel (marked in yellow), ethanol was replaced by n-butanol up to 50% by volume of ethanol
(minimum
(minimumvalue
valueregulated
regulatedby
byEN
EN15376),
15376),leading
leadingtotoaablend
blendofof50%
50%ethanol,
ethanol,35%
35%n-butanol,
n-butanol,and
and15%
15%
gasoline
by
volume.
This
submatrix
is
marked
with
blue
dots
in
Figure
1.
Third,
considering
gasoline by volume. This submatrix is marked with blue dots in Figure 1. Third, consideringagain
again
E85
E85asasaabaseline
baselinefuel,
fuel,gasoline
gasolinewas
wasprogressively
progressivelyreplaced
replacedby
byn-butanol
n-butanolup
uptoto15%
15%by
byvolume,
volume,thus
thus
removing
gasoline
from
the
blend.
This
submatrix
is
marked
with
green
dots
in
Figure
1. Finally,
removing gasoline from the blend. This submatrix is marked with green dots in Figure 1. Finally,
some
some
carried
outa for
a more
detailed
of vapor
pressure,
which
will
be explained
extraextra
dots dots
werewere
carried
out for
more
detailed
studystudy
of vapor
pressure,
which
will be
explained
in the
incorresponding
the corresponding
section.
These
extra
dots
are
marked
in
purple.
section. These extra dots are marked in purple.
Figure 1. Test matrix carried out in the experimental study.
Figure 1. Test matrix carried out in the experimental study.
Themain
maincharacteristics
characteristicsofofpure
purealcohols
alcohols(ethanol
(ethanoland
andn-butanol)
n-butanol)and
andgasoline
gasolineare
areshown
showninin
The
Table1.1.These
Theseselected
selectedresults
resultsare
areininagreement
agreementwith
withthose
thoseobtained
obtainedininthe
theliterature.
literature.For
Forinstance,
instance,
Table
thelower
lowerheating
heatingvalue,
value,the
thedensity,
density,and
andthe
thevapor
vaporpressure
pressureare
arevery
verysimilar
similartotothose
thoseobtained
obtainedby
by
the
Elfasakhany[20]
[20]and
andAleiferis
Aleiferisetetal.
al.[21]
[21]for
forethanol
ethanoland
andn-butanol
n-butanolfuels.
fuels.However,
However,the
thevapor
vaporpressure
pressure
Elfasakhany
valuesfor
for gasolines are
is aisseasonal
fuel,fuel,
so its
depend
on theon
season
values
arevariable,
variable,since
sincegasoline
gasoline
a seasonal
soproperties
its properties
depend
the
of the year.
experimental
procedure
and the and
devices
in this
to measure
properties
season
of theThe
year.
The experimental
procedure
the used
devices
usedstudy
in this
study to the
measure
the
describeddescribed
in the results
section
are
explained
below. Density
measured
following
EN ISO 3675
properties
in the
results
section
are explained
below.was
Density
was measured
following
EN
standard
at 15 ◦ C using
a densimeter.
A higher heating
wasvalue
measured
with a bomb
calorimeter
ISO
3675 standard
at 15 °C
using a densimeter.
A highervalue
heating
was measured
with
a bomb
(Parr 1351) (Parr
according
UNE 51123
standard.
vapor
pressure
was
measured
a temperature
calorimeter
1351)to
according
to UNE
51123Finally,
standard.
Finally,
vapor
pressure
wasatmeasured
at a
of 38 ◦ C withofa 38
commercial
(Eralytics,
model
Evarap EV01)
to EN according
13016-1. Research
temperature
°C with adevice
commercial
device
(Eralytics,
modelaccording
Evarap EV01)
to EN
Octane Number
formeasurements
gasoline, E10 (10%
ethanol E10
by volume
in gasoline
blend),
13016-1.
Research (RON)
Octanemeasurements
Number (RON)
for gasoline,
(10% ethanol
by volume
Bu16 (16%
n-butanol
by(16%
volume
in gasoline
blend)inwere
carried
out were
in a CFR
engine
inand
gasoline
blend),
and Bu16
n-butanol
by volume
gasoline
blend)
carried
out following
in a CFR
the ASTM
D 2699-15a
standard.
However,
a CFR engine
is outa of
range
whenisoperating
either
with
engine
following
the ASTM
D 2699-15a
standard.
However,
CFR
engine
out of range
when
pure alcohols
such
aspure
ethanol
or n-butanol
with blends
with high
alcohol
content.
thisalcohol
reason,
operating
either
with
alcohols
such asor
ethanol
or n-butanol
or with
blends
withFor
high
ethanolFor
andthis
n-butanol
were
from values
the literature
[18]. from the literature [18].
content.
reason,values
ethanol
andtaken
n-butanol
were taken
Withregard
regardtotofuels,
fuels,the
thegasoline
gasolineused
usedininthis
thisstudy
studywas
wassupplied
suppliedby
bythe
theRepsol
Repsolcompany,
company,and
and
With
itsmain
maincharacteristic
characteristicisisthe
theabsence
absenceofofoxygenated
oxygenatedadditives
additivessuch
suchasasETBE
ETBEand
andMTBE
MTBEininorder
ordertoto
its
properlyobserve
observethe
theeffect
effectofofalcohol
alcoholaddition.
addition.Butanol
Butanolwas
wassupplied
suppliedby
byGreen
GreenBiologics
BiologicsLtd.
Ltd.(Milton
(Milton
properly
Park,UK),
UK),asasaamember
memberofofthe
theConsortium
ConsortiumofofButanext
ButanextProject
Project(see
(seeAcknowledgments),
Acknowledgments),and
andethanol
ethanol
Park,
wassupplied
suppliedby
byPanReac
PanReacAppliChem.
AppliChem.
was
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Table 1. Specifications of tested fuels.
4 of 10
Ethanol a
n-Butanol a
Properties
Method
Gasoline a
Purity (% v/v)
99.5
99.5
Table 1. Specifications of tested fuels.
Density at 15 °C (kg/m3)
EN ISO 3675
726.0
793.0
808.7
Viscosity
at 40 °C (cSt)
EN
ISO 3104
0.40–0.80
1.08
2.63
Properties
Method
Gasoline a
Ethanol a
n-Butanol a
Higher heating value (MJ/kg)
UNE 51123
44.01
26.71
34.17
Purity (% v/v)
99.5
99.5
Higher at
heating
value3 (MJ/L)
31.95
21.18793.0
27.63808.7
EN ISO 3675
726.0
Density
15 ◦ C (kg/m
)
C 40
(%◦wt)
86.00
52.141.08
64.862.63
Viscosity at
C (cSt)
EN ISO 3104
0.40–0.80
Higher heating
(MJ/kg)
UNE 51123
44.01
H value
(% wt)
14.00
13.1326.71
13.5134.17
Higher heating
value
31.95
O (%
wt)(MJ/L)
0.00
34.7321.18
21.6227.63
C (% wt)
86.00
52.14
64.86
b
b
Fully miscible
<7.7 13.51
WaterHsolubility
EN ISO 12937
<0.1
(% wt) (ppm wt)
14.00
13.13
b
b
b
904
716
Standard enthalpy
of
vaporization
(kJ/kg)
380–500
O (% wt)
0.00
34.73
21.62
Water
solubility (ppm
wt) ratio
EN ISO 12937
Fully
<0.1 b
<7.7 b
Stochiometric
fuel/air
1/14.7
1/9.0 miscible 1/11.2
b
b
b
Standard enthalpy CFPP
of vaporization
(kJ/kg)
380–500
(°C)
EN116
<−51904
<−51716
Stochiometric fuel/air ratio
1/14.7
1/9.0
1/11.2
ASTM D-2699
95.8 c
107.0 d
96.0 d
Octane◦ number
CFPP ( C)
EN116
<−51
<−51
Vapor
pressure
(kPa)
EN
13016-1
60
15
2 96.0 d
Octane number
ASTM D-2699
95.8 c
107.0 d
point
(°C)
2719
−45.00
13.00 15
36.17 2
VaporFlash
pressure
(kPa)
ENISO
13016-1
60
◦ C)
a data measured
b
c
Flash point
(
ISO
2719
−
45.00
13.00
at University of Castilla-La Mancha; taken from reference [22]; data provided 36.17
by
a data measured at University
b taken from reference [22]; c data provided by Repsol
of Castilla-La
Mancha;
from Reference
[18].
Repsol company, Spain; d taken
company, Spain; d taken from Reference [18].
3. Results and Discussion
3. Results and Discussion
3.1. Density and Lower Heating Value
3.1. Density and Lower Heating Value
The density of blends is usually given by a volume-weighted average of the densities of the
The density of blends is usually given by a volume-weighted average of the densities of the
components (all measured at the same temperature). However, some exceptions to this behavior,
components (all measured at the same temperature). However, some exceptions to this behavior,
excess volume, can be found due to a large mismatch in the molecular/compositional structure of the
excess volume, can be found due to a large mismatch in the molecular/compositional structure of
components.
the components.
In this work, besides the test scheduled in the test matrices, some extra-blends were tested to
In this work, besides the test scheduled in the test matrices, some extra-blends were tested to
evaluate possible non-lineal tendencies when small quantities of oxygenated fuels were added with
evaluate possible non-lineal tendencies when small quantities of oxygenated fuels were added with
respect to the original test matrix. As observed in Figure 2, n-butanol has a higher density than
respect to the original test matrix. As observed in Figure 2, n-butanol has a higher density than ethanol,
ethanol, and both alcohols have a higher density than gasoline. In European countries, gasolines are
and both alcohols have a higher density than gasoline. In European countries, gasolines are usually
usually made to have densities close to the lower limit (upper and lower limits established in EN 228
made to have densities close to the lower limit (upper and lower limits established in EN 228 standard
standard are shown in Figure 2 with dashed lines) for two reasons: first, the strong dieselization of
are shown in Figure 2 with dashed lines) for two reasons: first, the strong dieselization of the vehicle
the vehicle market, leading to an extension of the diesel distillation range (and thus to an extension
market, leading to an extension of the diesel distillation range (and thus to an extension of the diesel
of the diesel density range); second, such a density allows for the further blending with oxygenates,
density range); second, such a density allows for the further blending with oxygenates, which usually
which usually have higher densities. In any case, only lower butanol concentrations with respect to
have higher densities. In any case, only lower butanol concentrations with respect to ethanol could be
ethanol could be used in the blends to fulfill the above-mentioned standard.
used in the blends to fulfill the above-mentioned standard.
Figure 2.
2. Density
Density versus
versus alcohol
alcohol content.
content.
Figure
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With regard
regard to heating
heating value, an
an almost linear
linear trend with
with the alcohol
alcohol content (Figure
(Figure 3)
3) can
can be
With
With
regard to
to heating value,
value, an almost
almost linear trend
trend with the
the alcohol content
content (Figure 3)
can be
be
observed when
when both
both ethanol
ethanol and
and n-butanol
n-butanol are
are used.
used. However,
However, n-butanol
n-butanol has aa higher
higher heating
heating value
value
observed
observed
when both
ethanol and
n-butanol are
used. However,
n-butanol has
has a higher heating
value
than ethanol
ethanol in both
both mass
mass and
and volume
volume basis,
basis, as
as observed
observed in
in Figure
Figure 3.
3. For
For this
this reason,
n-butanol blends
blends
than
reason, n-butanol
n-butanol
than
ethanol in
in both mass
and volume
basis, as
observed in
Figure 3.
For this
reason,
blends
are
expected
to
reduce
the
fuel
consumption
in
an
SIE
vehicle
with
respect
to
ethanol
blends
[3],
and
are expected
an SIE
vehicle with
with respect
respect to
ethanol blends
blends [3],
[3], and
and
are
expected to
to reduce
reduce the
the fuel
fuel consumption
consumption in
in an
SIE vehicle
to ethanol
would thereforeincrease
increase the
vehicle´s
mileage.
The
effect
of alcohol
as a fuel component
on the
would
vehicle´s
mileage.
TheThe
effect
of alcohol
as a fuel
on the on
engine
would therefore
therefore increasethe
the
vehicle´s
mileage.
effect
of alcohol
as acomponent
fuel component
the
engine
efficiency
has
been
reported
to
be
minor
[3,17,20]
and
is
not
expected
to
modify
this
trend.
efficiency
has
been
reported
to
be
minor
[3,17,20]
and
is
not
expected
to
modify
this
trend.
engine efficiency has been reported to be minor [3,17,20] and is not expected to modify this trend.
Figure 3.
3. Heating
Heating value
value versus
versus alcohol
alcohol content
content in
in mass basis
basis and volume
volume basis.
Figure
Figure
3. Heating
value versus
alcohol content
in mass
mass basis and
and volume basis.
basis.
As shown in Figure 4, when the ethanol content increases, the octane number of the blend also
As shown in Figure 4, when the ethanol content increases, the octane number of the blend also
increases. This could derive into an advantage, either because the compression ratio of the engine
This could
could derive
derive into
into an advantage,
advantage, either because
because the compression ratio of the engine
increases. This
could be increased in a modified engine design, leading to improved engine efficiency, or because
could be increased in a modified engine design, leading to improved engine efficiency, or because
additives improving the octane number could be avoided. Differently to ethanol, butanol presents a
improving the
the octane
octane number
numbercould
couldbe
beavoided.
avoided.Differently
Differentlytotoethanol,
ethanol,butanol
butanolpresents
presents
additives improving
a
similar value of octane number compared to gasoline and, thus, modifying the butanol content in
a similarvalue
valueofofoctane
octanenumber
numbercompared
comparedtotogasoline
gasolineand,
and,thus,
thus, modifying
modifying the
the butanol
butanol content in
similar
gasoline blends would not require re-design nor a reformulation of additives. Consequently, butanol,
require re-design nor aa reformulation
reformulation of
of additives.
additives. Consequently,
Consequently, butanol,
butanol,
gasoline blends would not require
compared to ethanol, can be considered as more interchangeable with gasoline.
compared to ethanol, can be considered
considered as
as more
more interchangeable
interchangeable with
with gasoline.
gasoline.
Figure 4. Octane number of ethanol and butanol blends with gasoline.
Figure 4. Octane number of ethanol and butanol blends with gasoline.
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3.2. Vapor Pressure
With Pressure
regard to vapor pressure, four standards were used for the vapor pressure tests.
3.2. Vapor
Specifically, two American standards (ASTM D5191 and ASTM D6378) and two European standards
With regard to vapor pressure, four standards were used for the vapor pressure tests. Specifically,
(EN 13016-1 and EN 13016-2) were followed. Standard EN 13016-1 was selected because gasoline
two American standards (ASTM D5191 and ASTM D6378) and two European standards (EN 13016-1
standard EN 228 indicates that vapor pressure tests must be made at 37.8 °C. This standard allows
and EN 13016-2) were followed. Standard EN 13016-1 was selected because gasoline standard EN 228
for a vapor pressure increase when gasoline is replaced by
ethanol up to 10% by volume as shown in
indicates that vapor pressure tests must be made at 37.8 ◦ C. This standard allows for a vapor pressure
Table 2. This increase is motivated by its azeotropic behavior.
increase when gasoline is replaced by ethanol up to 10% by volume as shown in Table 2. This increase
With regard to Submatrix 1, a sharp decrease in vapor pressure is observed in Figure 5 when
is motivated by its azeotropic behavior.
ethanol is replaced by n-butanol keeping the oxygen concentration constant. This decrease is
With regard to Submatrix 1, a sharp decrease in vapor pressure is observed in Figure 5 when
observed for all oxygen limitations. This drop is due mainly to the lower vapor pressure of n-butanol
ethanol is replaced by n-butanol keeping the oxygen concentration constant. This decrease is observed
compared to that of ethanol. It can be observed that such a decrease is more effective for lower oxygen
for all oxygen limitations. This drop is due mainly to the lower vapor pressure of n-butanol compared
content than for high oxygen content. Nevertheless, substantial decreases in vapor pressure would
to that of ethanol. It can be observed that such a decrease is more effective for lower oxygen content
require high n-butanol contents (and thereby O2 content).
than for high oxygen content. Nevertheless, substantial decreases in vapor pressure would require
high Table
n-butanol
contents
(and
thereby
O2 content).
2. Vapor
pressure
overrun
authorized
by the EN 228 standard for different ethanol additions.
Ethanol
Content
(% authorized
v/v) Authorized
Pressure
Overrunethanol
(kPa) additions.
Table 2. Vapor
pressure
overrun
by the ENVapor
228 standard
for different
0
Ethanol Content
(% v/v)
1
2 0
3 1
4 2
3
5 4
6 5
7 6
8 7
8
9
9
10 10
0
Authorized Vapor
3.7Pressure Overrun (kPa)
6
7.2
7.8
8
8
7.9
7.9
7.8
7.8
0
3.7
6
7.2
7.8
8
8
7.9
7.9
7.8
7.8
Figure 5.
5. Vapor
Vapor pressure
pressure versus
versus percentage
percentage of
of n-butanol
n-butanol in
in Submatrix
Submatrix 1.
1.
Figure
Following
Following EN
EN 228
228 standard,
standard, summer
summer vapor
vapor limits
limits were
were defined
defined between
between 45
45 and
and 60
60 kPa,
kPa, whereas
whereas
winter
between 50
50 and
and 80
80 kPa
kPa (shown
(shown in
in Figure
Figure 66 with
with aa shaded
shaded area).
area).
winter limits
limits were
were established
established between
Sustainability 2017, 9, 589
Sustainability 2017, 9, 589
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7 of 10
7 of 10
7 of 10
All
the
gasoline–ethanol–butanol blends tested
tested Submatrix
Submatrix 1 fulfill
the
vapor
pressure
limits
AllAll
thethe
gasoline–ethanol–butanol
fulfillthe
thevapor
vaporpressure
pressure
limits
gasoline–ethanol–butanolblends
blends tested in
in Submatrix 11fulfill
limits
established
in
the
EN
228
standardfor
forthe
thewinter
winterseason
season (as
(as shown
in
Figures
55and
6),
sosocold-start
established
in
the
EN
228
standard
shown
in
Figures
and
6),
cold-start
established in the EN 228 standard for the winter season (as shown in Figures 5 and 6), so cold-start
problems
should
not
arise.
problems
should
notnot
arise.
problems
should
arise.
Figure
6.Vapor
Vapor pressurerange
range (shaded area)
area) accepted by
EN
228
in
winter.
Figure
6.6.
by EN
EN228
228in
inwinter.
winter.
Figure
Vaporpressure
pressure range(shaded
(shaded area) accepted
accepted by
On the other hand, vapor pressure limitation is more restrictive in summer, as shown in Figures
On
theother
other hand,
vapor
pressure
limitation
is more
in summer,
shown inas
Figures
On
the
hand,
vapor
pressure
limitation
is restrictive
more
restrictive
in as
summer,
shown
5 and 7.
None of the
gasoline–ethanol
blends
would fulfill
EN 228
requirements
unless the vapor
5
and
7.
None
of
the
gasoline–ethanol
blends
would
fulfill
EN
228
requirements
unless
the
vaporthe
in Figures
5
and
7.
None
of
the
gasoline–ethanol
blends
would
fulfill
EN
228
requirements
unless
pressure overrun (shown in Table 2) is considered. On the contrary, gasoline–n-butanol blends fulfill
pressure
overrun
(shown
in Table
2) is considered.
On theOn
contrary,
gasoline–n-butanol
blends fulfill
vapor
overrun
(shown
inlower
Table
2) is considered.
the
contrary,
gasoline–n-butanol
blends
the pressure
EN 228 standard
for much
alcohol
concentrations
compared
to
ethanol, so no overrun
the
EN
228
standard
for
much
lower
alcohol
concentrations
compared
to
ethanol,
so
no
overrun
fulfill
the EN 228would
standard
for muchItlower
alcoholto
concentrations
compared
ethanol,bysothe
noRepsol
overrun
authorization
be needed.
is important
remark that the
gasolineto
donated
authorization would be needed. It is important to remark that the gasoline donated by the Repsol
authorization
be needed. It is
remarknot
that
the gasoline
by the Repsol
company is would
a fuel commercialized
in important
winter and to
therefore
prepared
for usedonated
in the summer.
company is a fuel commercialized in winter and therefore not prepared for use in the summer.
company is a fuel commercialized in winter and therefore not prepared for use in the summer.
Figure
7.
Vapor pressurerange
range (shadedarea)
area) accepted by
EN
228
in
the
summer.
Figure
7. 7.
Vapor
by EN
EN 228
228in
inthe
thesummer.
summer.
Figure
Vaporpressure
pressure range(shaded
(shaded area) accepted
accepted by
Sustainability 2017, 9, 589
8 of 10
Sustainability
2017,
589
88 of
10
Sustainability
2017,
589 blends (Submatrices 2 and 3), when 15% (volume basis) of gasoline
ofis
10 kept
With
regard
to9,9,E85
constant (Figure
8, squared
symbols and Figure
9, blue
dots), and
butanol content
is increased
to
With
With regard
regard to
to E85
E85 blends
blends (Submatrices
(Submatrices 22 and
and 3),
3), when
when 15%
15% (volume
(volume basis)
basis) of
of gasoline
gasoline is
is kept
kept
replace
ethanol
by up8,
50% (volume
according
todots),
the EN
limits,
lower
vapor pressure
constant
(Figure
squared
symbols
and
9,
and
butanol
content
is
to
constant
(Figure
8,to
squared
symbolsbasis)
and Figure
Figure
9, blue
blue
dots),
and15376
butanol
content
is increased
increased
to
values
are
obtained.
This
means
that
replacing
ethanol
by
n-butanol
in
E85
blends
could cause
replace
replace ethanol
ethanol by
by up
up to
to 50%
50% (volume
(volume basis)
basis) according
according to
to the
the EN
EN 15376
15376 limits,
limits, lower
lower vapor
vapor pressure
pressure
cold-start
problems
despite
lower
enthalpy
vaporization
of butanol,
and
due
to the
lower
vapor
values
are
This
means
that
replacing
by
in
could
cause
coldvalues
are obtained.
obtained.
Thisthe
means
that
replacingofethanol
ethanol
by n-butanol
n-butanol
in E85
E85 blends
blends
could
cause
coldstart
problems
despite
the
enthalpy
of
butanol,
and
the
vapor
pressure
n-butanol
[4,23–25].
When
n-butanol
substitutesof
symbols
startof
problems
despite
the lower
lower
enthalpy
of vaporization
vaporization
ofgasoline
butanol,(Figure
and due
due8,to
totriangle
the lower
lower
vapor and
pressure
of
[4,23–25].
When
substitutes
8,
symbols
and
pressure
of n-butanol
n-butanol
[4,23–25].problems
When n-butanol
n-butanol
substitutes
gasoline
(Figure
8, triangle
trianglethus
symbols
and
Figure
9, green
dots), cold-start
are expected
to gasoline
be
even(Figure
more relevant,
requiring
a
Figure
9,
green
dots),
cold-start
problems
are
expected
to
be
even
more
relevant,
thus
requiring
a
Figure
9,
green
dots),
cold-start
problems
are
expected
to
be
even
more
relevant,
thus
requiring
a
second fuel tank with a more volatile fuel for the start. This drawback is expected to be less relevant in
second
tank
aa more
volatile
fuel
the
This
is
be
second fuel
fuel engines
tank with
withdue
more
volatile
fuel for
forcylinder
the start.
start.pressure
This drawback
drawback
is expected
expected to
toconditions.
be less
less relevant
relevant
direct-injection
to the
increased
and temperature
Indeed,
in
in direct-injection
direct-injection engines
engines due
due to
to the
the increased
increased cylinder
cylinder pressure
pressure and
and temperature
temperature conditions.
conditions. Indeed,
Indeed,
as can be observed in Figure 9 (shaded area), the replacement of either gasoline or ethanol by n-butanol
as
as can
can be
be observed
observed in
in Figure
Figure 99 (shaded
(shaded area),
area), the
the replacement
replacement of
of either
either gasoline
gasoline or
or ethanol
ethanol by
by nnwould
move the blend
out of
the limits
established
by the EN
1537615376
standard. ForFor
this reason,
some
butanol
butanol would
would move
move the
the blend
blend out
out of
of the
the limits
limits established
established by
by the
the EN
EN 15376 standard.
standard. For this
this reason,
reason,
extra some
blends
were
tested
using
E70
(70%
ethanol
and
30%
gasoline)
as
a
baseline
fuel.
In
this
case,
some extra
extra blends
blends were
were tested
tested using
using E70
E70 (70%
(70% ethanol
ethanol and
and 30%
30% gasoline)
gasoline) as
as aa baseline
baseline fuel.
fuel. In
In this
this the
replacement
of
ethanol
(up
to
50%
by
volume
according
to
the
EN
15376
standard
limits)
by
case,
by
case, the
the replacement
replacement of
of ethanol
ethanol (up
(up to
to 50%
50% by
by volume
volume according
according to
to the
the EN
EN 15376
15376 standard
standard limits)
limits)butanol
by
keeping
the gasoline
content
constant
forallows
the fulfillment
of the EN
15376
(Figure 9)
butanol
keeping
gasoline
content
constant
for
of
EN
15376
butanol
keeping the
the
gasoline
contentallows
constant
allows
for the
the fulfillment
fulfillment
of the
the
ENstandard
15376 standard
standard
(Figure
9)
the
decrease
in
pressure
(circle
symbols,
(Figure
9) despite
despitein
the
decrease
in vapor
vapor
pressure
(circleFigure
symbols,
Figure 8).
8).
despite
the decrease
vapor
pressure
(circle
symbols,
8).Figure
Figure
8.
pressure
versus
percentage
Submatrices
22 and
3.
Figure
8. Vapor
Vapor
pressure
versuspercentage
percentage of
n-butanol
inin
Submatrices
and
3. 3.
Figure
8. Vapor
pressure
versus
of n-butanol
n-butanolin
Submatrices
2 and
Figure 9. Vapor pressure range (shaded area) accepted by CEN/TS 15293/2011.
Figure
9. Vapor
pressure
range
(shadedarea)
area)accepted
accepted by
15293/2011.
Figure
9. Vapor
pressure
range
(shaded
byCEN/TS
CEN/TS
15293/2011.
Sustainability 2017, 9, 589
9 of 10
4. Conclusions
The main properties established in standards EN228 (for gasoline fuels) and CEN/TS 15293/2011
(for E85 blends) were measured for n-butanol–ethanol–gasoline blends and butanol–E85 blends. Fuels
used in SIEs can contain up to 3.7% O2 by mass to be commercialized. In this frame, the substitution of
ethanol (up to 10% by volume) by n-butanol (up to 16% by volume) presents a series of benefits such
as a higher heating value or a lower hygroscopic tendency compared to ethanol blends, which makes
n-butanol a promising fuel for SIEs. The higher heating value for butanol–gasoline blends would
reduce the engine fuel consumption. When butanol is blended with gasoline, the vapor pressure
decreases, and consequently, the blends fulfill EN 228.
However, the use of n-butanol in E85 blends substituting either gasoline or ethanol can cause
cold-start problems despite the lower enthalpy of vaporization of n-butanol. To avoid these problems,
ternary blends where both gasoline and ethanol are simultaneously replaced with n-butanol should
be used. As an example, if the baseline fuel is E70 (70% ethanol and 30% gasoline by volume), any
replacement of ethanol by n-butanol would fulfill EN 15376, and cold-start problems should therefore
not arise.
Acknowledgments: This research was co-funded by the European Union Horizon 2020 Research and Innovation
Programme under grant agreement No. 640462 (ButaNext project). Repsol and Green Biologics are gratefully
acknowledged for the donation of diesel and n-butanol fuels, respectively.
Author Contributions: Magín Lapuerta conceptualized the study and organized the manuscript,
Rosario Ballesteros conducted and processed the experiments and revised the laboratory conditions, Javier Barba
processed the experiments and wrote the manuscript. All authors edited and approved the manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
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