The main interest of this research was to formulate highly stable, oxygenated water-in-diesel emulsion that gives minimum hazardous exhaust emission. Fatty acid methyl esters (FAME) are found to be very viable oxygenate amongst other four oxygenated components. The oxygenated W/D emulsion is formulated using 20% FAME, 10% water, and 5% blend of Span 80/Tween 80 and diesel. The properties of this oxygenated fuel emulsion are investigated. Though the viscosity of fuel is found to be increased, it is within the standard limit value. There is an improvement in oxygenated fuel emulsion in burning test, evaporation rate test, and calorific value.

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Formulation of Oxygenated Water-in-
diesel Fuel Emulsion and Investigation of
Its Properties
H. Patil
a
, A. Gadhave
a
, S. Mane
a
& J. Waghmare
b
a
Institute of Chemical Technology, Nathalal Parekh Road, Matunga
East, Mumbai, Maharashtra, India
b
Department of Oils, Oleochemicals and Surfactant Technology,
Institute of Chemical Technology, Nathalal Parekh Road, Matunga
East, Mumbai, Maharashtra, India
Published online: 20 Dec 2014.
To cite this article: H. Patil, A. Gadhave, S. Mane & J. Waghmare (2015) Formulation of Oxygenated
Water-in-diesel Fuel Emulsion and Investigation of Its Properties, Petroleum Science and Technology,
33:2, 211-217, DOI: 10.1080/10916466.2014.960527
To link to this article: http://dx.doi.org/10.1080/10916466.2014.960527
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3. Petroleum Science and Technology, 33:211–217, 2015
Copyright C Taylor & Francis Group, LLC
ISSN: 1091-6466 print / 1532-2459 online
DOI: 10.1080/10916466.2014.960527
Formulation of Oxygenated Water-in-diesel Fuel Emulsion
and Investigation of Its Properties
H. Patil,1
A. Gadhave,1
S. Mane,1
and J. Waghmare2
1
Institute of Chemical Technology, Nathalal Parekh Road, Matunga East, Mumbai,
Maharashtra, India
2
Department of Oils, Oleochemicals and Surfactant Technology, Institute of Chemical Technology,
Nathalal Parekh Road, Matunga East, Mumbai, Maharashtra, India
The main interest of this research was to formulate highly stable, oxygenated water-in-diesel emulsion
that gives minimum hazardous exhaust emission. Fatty acid methyl esters (FAME) are found to be
very viable oxygenate amongst other four oxygenated components. The oxygenated W/D emulsion is
formulated using 20% FAME, 10% water, and 5% blend of Span 80/Tween 80 and diesel. The properties
of this oxygenated fuel emulsion are investigated. Though the viscosity of fuel is found to be increased,
it is within the standard limit value. There is an improvement in oxygenated fuel emulsion in burning
test, evaporation rate test, and calorific value.
Keywords: oxygenated agents, water-in-diesel emulsion, stability, combustion, viscosity
1. INTRODUCTION
The major contributor of today’s world energy source is transportation. Large amounts of fuels
have been utilized commercially. Because of the high thermal efficiency and fuel economy, diesel
is gaining more attention. It is widely used in heavy vehicles, marine, and industrial process plants.
But the rising fuel costs and inflexible government regulations drive researchers’ attention to find
new solutions for high fuel efficiency with minimum exhaust gas emissions. The exhaust gas mainly
contains NOx, particulate matters, unburned carbon, and CO (Pischinger, 1998). These are highly
health hazardous and air polluting components.
Introduction of water into diesel can reduce the NOx formation and particulate matters emission
(Muzio and Quartucy, 1997; Joshi and Pegg, 2007). But the introduction of direct water into diesel
engine increases the CO and CO2 formation. Thus, to overcome this problem, water-in-diesel
emulsion fuels have been developed. In these fuels, water is dispersed into the diesel with the help
of surfactant. It has been reported that emulsion fuels lowers soot formation, NOx and particulate
matter emission (Qi et al., 2010). Emulsion method is one of the possible directions to enhance the
fuel economy with reducing hazardous emission. Though emulsion fuels enhance the CO emission,
it can be reduced by introducing oxygenated compounds into emulsion system (Lin and Wang,
2004).
Address correspondence to J. Waghmare, Department of Oils, Oleochemicals and Surfactant Technology, Institute
of Chemical Technology, Nathalal Parekh Road, Matunga East, Mumbai -400019, Maharashtra, India. E-mail: jyotsna.
waghmare@gmail.com
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lpet.
211
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4. 212 H. PATIL ET AL.
Several studies have shown significant reduction in PM emissions from diesel engines when
oxygenates were blended with conventional diesel fuels (Lin and Wang, 2004; Stoner and Litzinger,
1999). The mechanism for the effect of oxygenates on soot formation is not known. Various types of
oxygenating compounds including ethers, alcohols, carbonates, acetals and esters have been tested
in engines to determine the effects of oxygenates on exhaust emissions. Oxygenates range from
light molecules such as ethanol to heavy methyl esters of vegetable oils with up to 20 carbon atoms.
Stoner and Litzinger (1999) hypothesized that oxygenates would tend to form CO prematurely in
the reaction zone. They proposed that CO would react with free radicals such as H•
and •
CH3 to
interfere with the precursor reactions that lead to soot formation. Miyamoto (2000) investigated
the effect of several oxygenates on emission from four-stroke direct injected single cylinder engine
and compare pure fuel emission with blended diesel-oxygenate fuel. Miyamoto found that smoke
emission is reduced significantly by increasing the oxygenated load.
Further promising approach to reduce PM emissions by modifying the fuel composition involves
the addition of oxygenated compounds to the normal diesel fuel. Fuel additives and blends have been
investigated to limit the increase in PM emissions that often accompanies the reduction in NO (Lin
and Wang, 2004). Oxygen can be added to the fuel bound to various molecular structures such as
alcohols, carbonates, acetates, glycols, and esters. There have been many studies that probe how each
of these might influence exhaust emissions (Lin and Wang, 2006; Senthil Kumar et al., 2006; Qi et al.,
2010). While these studies used a variety of test engines, testing cycles, and diagnostic methods,
they consistently found a significant reduction of particulate emissions that has been correlated to
the amount of oxygen added However, the conclusions differ related to the significance of the type
of oxygenate used. Oxygenated fuel inhibits the particle growth and lowers the particle number. It
has been reported that addition of oxygenated hydrocarbons reduces the production of a postignition
soot precursor. When overall oxygen content in fuel reached approximately 30–40%, production of
soot precursors falls effectively to zero. Further, 1,1-diethoxyethane, briefly named as acetal, lowers
the CO2 emission.
The main focus of this research is to formulate oxygenated W/D fuel emulsion and to analyze
physical properties of that fuel emulsion. We first determined the appropriate composition of diesel
and oxygenate to make suitable fuel emulsion and then emulsification characteristics, and fuel
properties of the blends at different blending compositions were investigated. Further, effect of
oxygenated compound on emulsion preparation, homogeneity, stability, and physical properties
were also analyzed.
2. EXPERIMENTAL
2.1 Materials
The nonionic surfactants Tween 80 and Span 80 were supplied by Unitochemical Pvt. Ltd., and Croda
India Pvt. Ltd., respectively. Tween 80, polyoxyethylene sorbitan monooleate, is a hydrophilic agent
with HLB = 15. Span 80, sorbitan monooleate, is a lipophilic agent with HLB = 4.3. Oxygenated
components, ethanol, methanol, fatty acid methyl esters (FAME), acetaldehyde, and ethyl acetate
were purchased from Thomas Baker.
Diesel no. 2 was purchased from local gas station. The technical characteristics of diesel were
analyzed. It had density of 845.8 Kg/m3
at 15◦
C whereas the kinematic viscosity was 3.268 cSt at
40◦
C. The pour and the flash point observed were 2◦
C and 53◦
C, respectively. The cetane number
was found to be 53.
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5. OXYGENATED WATER-IN-DIESEL FUEL EMULSION 213
TABLE 1
Physical Properties of Oxygenated Compounds
No. Oxygenated Compounds Chemical Formula Density, kg/m3 Oxygen Content, wt% Flash Point, ◦C
1 Acetaldehyde CH3CHO 788 36.3 –26
2 Ethanol CH3CH2OH 794 34.7 16
3 Ethyl acetate CH3[C O]OCH2CH3 902 36.3 7
4 Methanol CH3OH 813 49.9 11
5 FAME RCOOCH3 840 60.3 130
2.2 Methods
2.2.1 Preparation of oxygenated fuel emulsion
The blend of Span 80 and Tween 80 (Span80/Tween80) was prepared. The blend was having HLB
= 9. The distilled water was used in fuel emulsion. Homogenizer was used to develop emulsion.
Fuel emulsion was prepared in two steps:
1. Required quantity of suitable oxygenated component was mixed with diesel. Surfactant blend
was mixed with a diesel oxygenated mixture with stirring. Pre-emulsion was then prepared
by addition of water to a mixture of blended surfactant and diesel oxygenated solution.
The rate of addition of water was kept constant with constant stirring rate at 800 rpm. The
concentration of surfactant blend in total emulsion solution was 5%.
2. In the second step, the prepared pre-emulsion were stirred at high speed of 5000 rpm for
20 min. All experiments were run at room temperature.
3. RESULTS AND DISCUSSION
The initial criteria used to screen out the viable oxygenate candidates were (a) The amount of
oxygenate added to diesel fuel to give 7 wt% oxygen should not exceed 20 vol%; (b) the flash point
should not be less than 42◦
C, which is the specification of diesel fuel; (c) oxygenate should be
soluble in diesel fuel at temperatures down to 6◦
C and tolerate at least 1000 ppm of water, and (d)
oxygenate must not decompose into corrosive products. The data for criteria a and b were obtained
from the literature and are summarized in Table 1, whereas criteria c and d had to be measured and
given in Table 2.
The data from Table 1 and 2 suggest that ethanol, methanol, and FAME follow more criteria from
all the five oxygenated components. As ethanol, methanol, and FAME have solubility in diesel, they
TABLE 2
Analysis of Oxygenated Compounds
No. Oxygenated Compounds Solubility Corrosion Emulsification
1 Acetaldehyde No No No
2 Ethanol Yes No No
3 Ethyl acetate No No No
4 Methanol Yes No No
5 FAME Yes No Yes
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6. 214 H. PATIL ET AL.
TABLE 3
Homogeneity Test of Oxygenated Emulsions With Randomly Varied Compositions
Components
Batch No. Diesel,% Ethanol,% Methanol,% FAME,% Description Stability, days
1 95 5 0 0 Separated phase <1
2 90 10 0 0 Separated phase <1
3 85 15 0 0 Separated phase <1
4 80 20 0 0 Separated phase <1
5 95 0 5 0 Separated phase <1
6 90 0 10 0 Separated phase <1
7 85 0 15 0 Separated phase <1
8 80 0 20 0 Separated phase <1
9 95 0 0 5 Homogenous blend 30
10 90 0 0 10 Homogenous blend 30
11 85 0 0 15 Homogenous blend 30
12 80 0 0 20 Homogenous blend 30
13 70 10 0 20 Homogenous blend 20
14 70 0 10 20 Separated phase <1
15 70 5 0 25 Homogenous blend 25
were selected for the homogeneity test. Various compositions of blend of diesel and oxygenated
components were formulated and labeled them as BATCH 1 to BATCH 15. No water is present in
these formulations. Table 3 shows the compositions and their stability data.
BATCH 1–8 and BATCH 14 emulsions showed phase separation within one day whereas other
emulsions showed very good homogeneity with high emulsion stability. Those emulsions were stable
for almost 30 days. There was no agglomeration of liquid droplets or sedimentation occurred. The
phase separation is due to the fact that the presence of water in hydrous ethanol has a strong polarity
while diesel is a nonpolar solvent. As FAME possesses hydrophilic and hydrophobic properties, it
acts as an emulsifier that increases the stability of emulsions. The results also show that the stability of
diesel and oxygenated blends increases as the amount of FAME (also called as a biodiesel) increases.
The presence of FAME shows the surfactant property that defers the maximum permissible water
content by developing a microemulsion between organic phases. The alignment of the amphiphilic
structures of FAME at the diesel/ethanol-water interface can reinforce the structural affinity among
the various components mixtures.
Two formulations (BATCH 12 and BATCH 15) were considered as best among all the formulations
and were chosen to develop oxygenated W/D emulsions. Figure 1 shows the pattern of lowering
FIGURE 1 Oxygenated W/D emulsion stability (days).
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7. OXYGENATED WATER-IN-DIESEL FUEL EMULSION 215
TABLE 4
Evaporation Test for Oxygenated W/D Emulsion
Room Temperature (30◦C) Room Temperature (60◦C)
100% W/D Emulsion Oxygenated W/D 100% W/D Emulsion Oxygenated W/D
No. Time, h Diesel,% (Without Oxygenate) Emulsion (%) Diesel (%) (Without Oxygenate) Emulsion,%
1 1 3 0.5 0.5 42 5 4
2 2 5 1.53 1.5 55 10 8.5
3 3 7 1.5 1.45 62 15 13
4 4 8 1.75 1.7 70 20 18
5 5 9 1.93 1.85 77 30 28
6 6 11 2 1.8 80 40 39
the stability of oxygenated fuel emulsions of BATCHES 12 and 15 with increasing water content.
Figure 1 shows that both W/D emulsions follow almost same pattern and the lowering rate is quite
sluggish up to 20% water content. But beyond 20% water content, the pattern shoots down.
After formulating homogenous, stable oxygenated W/D emulsion, it is very important to investi-
gate its physical properties to understand its compatibility with various conditions that are bound to
be there in application processes.
It was found from Table 3 and Figure 1 that BATCH 12 containing 80% diesel and 20% FAME
forms more stable W/D emulsion that that of BATCH 15 containing (70% diesel, 5% ethanol,
25% FAME). Therefore, BATCH 12 was selected to make final stable W/D emulsion. The stable
oxygenated W/D emulsion was formulated with 10% water content.
Viscosity is one of the most important characteristics in fuel emulsion as this decides the flow
of fuel into diesel engine. The viscosity of pure diesel, oxygenated diesel and oxygenated water-
in-diesel (W/D) emulsion was measured. It was found that viscosity increased with 20% addition
of FAME and it was then further increased by incorporating 10% water. The measured values are
3.2 cSt, 3.72 cSt, and 4.1 cSt for pure diesel, oxygenated diesel, and oxygenated W/D emulsion,
respectively. Though the increased value is quite high if compared with pure diesel, it comes under
standard limit value of ASTM specification D975. Therefore, oxygenated W/D emulsion could be
used as a standard fuel.
Fuel faces many environmental, transportation, or storage conditions. Temperature is the most
affecting factor of these conditions. Therefore, thermal stability needs to be investigated. The
oxygenated W/D emulsion containing 20% FAME (v/v) and 10% water (v/v) was kept at different
temperatures and checked their stability. The oxygenated W/D emulsion possesses very good thermal
stability. The emulsion was stable for five days at all the temperature ranging from –4◦
C to 50◦
C.
Fuel transportation is an unavoidable process. Fuel has to be transported from gas station to target
place. Further, during applications such as vehicles and industrial power plants, fuel constantly
faces sloshes and vibrations. Sometimes sloshes are too high. Therefore, it is mandatory to check
the compatibility of oxygenated W/D emulsion with slosh and vibrations. It was observed that
oxygenated fuel emulsion was stable for 24 h under constant sloshes and vibrations.
Since the diesel contains low carbon chain compounds, they get easily evaporated even at room
temperature. Large amount of fuel gets wasted just because of evaporation. Therefore, one must
perform evaporation rate test of fuel. We tested the oxygenated fuel emulsion for evaporation rate at
room temperature (30◦
C) and 60◦
C and compared it with pure diesel. 10 ml of each pure diesel and
oxygenated fuel emulsion were taken in Petri dish and kept at 30◦
C and 60◦
C for 6 h. The percentage
of evaporation was checked after each hour. The investigated data are compiled in Table 4.
Burning test was performed to investigate burning capacity of the oxygenated diesel emulsion
and compare it with pure diesel and diesel emulsion. It was found that water-in-diesel emulsion
required maximum time for complete burning than other two fuels. As expected, pure fuel burned
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8. 216 H. PATIL ET AL.
more quickly than other two emulsions. Oxygenated W/D emulsion took more time (20 sec more)
than that of pure fuel and quite less time than that of diesel emulsion. The time difference between
two fuel emulsions is about 20 sec. This is because of the presence of oxygenates (i.e., FAME).
FAME is highly susceptible to fire. It helps to burn the fuel. So, it reduces the burning time of fuel
emulsion by 20 sec. But as water is present, it took 20 sec more than pure diesel.
The calorific value of fuel is a measure of heat generated during combustion of fuel at constant
temperature and pressure. To analyze the efficiency of the fuel or fuel emulsion, the calorific value
needs to be determined. We used an automatic adiabatic bomb calorimeter to determine the calorific
value of oxygenated diesel emulsion and diesel emulsion (without oxygenate) and compare them
with pure fuel. The calorific values of oxygenated diesel emulsion and diesel emulsion were found to
be 40,200 kJ/kg and 39,700 kJ/kg, respectively. These values are quite less than pure diesel (44,400
kJ/kg). This is because of the presence of water in fuel, which lowers the calorific value. The water
present in the fuel forms “heat sink.” Heat sink is a phenomenon in which water content in an
emulsion absorbs the heat generated during combustion of fuel and thus reduces the calorific value.
It can easily be concluded that increase in calorific value of oxygenated diesel emulsion is because
of the presence of oxygenated agent (i.e., FAME). It helps in the combustion process of fuel and
thus more heat is released.
4. CONCLUSION
The aim of developing oxygenated W/D emulsion is successfully achieved. FAME is the only
oxygenate that was found to be viable oxygenate amongst other four oxygenates used for the
study. It forms stable and homogenous blend with pure diesel. Therefore, it is used to make most
stable oxygenated W/D fuel emulsion. The effects of oxygenated FAME addition on water-in-diesel
emulsion characteristics are investigated and summarized as follows:
Addition of oxygenate increases the viscosity of pure diesel. Same is the case with W/D emulsion.
Though the addition of oxygenate (i.e., FAME) raises the viscosity of diesel, it comes under standard
limit value (1.7–4.1). Therefore, oxygenated fuel emulsion can be used as a fuel.
The oxygenated W/D emulsion containing 20% FAME and 10% water is thermally stable at
temperature range of –4◦
C to 50◦
C for five days. It also possesses high slosh and vibration stability.
The evaporation rate of oxygenated W/D emulsion is very low as compared to pure diesel. It is
also lower than that of fuel emulsion having no oxygenates. FAME is a long hydrocarbon chain.
Therefore, it restricts the evaporation rate of diesel.
Burning test shows that oxygenated fuel emulsion takes more time to burn than pure fuel, but less
time than fuel emulsion having no oxygenates. Though presence of water affects burning ability,
excess of oxygen in oxygenated fuel emulsion helps in burning. Therefore, it is a sandwich between
pure fuel and fuel emulsion (without oxygenate).
Water affects the calorific value of diesel. Therefore, oxygenated fuel emulsion and fuel emulsion
(without oxygenate) possess less calorific value than that of pure fuel. Water absorbs heat produced
during combustion. But the presence of oxygenate (i.e., FAME) encourages the combustion process.
It results in an increase in heat generated from combustion. So, though presence of water affects the
calorific value, increase in combustion increases the overall heat and thus calorific value.
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