This document summarizes research on the effect of water content on partial ternary phase diagrams of water-in-diesel microemulsion fuels. Water-in-diesel microemulsions were prepared with varying water content from 5-20% by weight. As water content increased, the region of microemulsion formation decreased on the phase diagrams. Higher water content also led to increased droplet size and viscosity of the microemulsions over time, as well as decreased stability of the microemulsion systems. The optimum microemulsion compositions were identified at 20% surfactant and 15% co-surfactant concentrations.

1. Effect of water content on partial ternary phase diagram water-in-diesel microemulsion
fuel
Hastinatun Mukayat, Khairiah Haji Badri, Ismail Ab. Raman, and Suria Ramli
Citation: AIP Conference Proceedings 1614, 256 (2014); doi: 10.1063/1.4895205
View online: http://dx.doi.org/10.1063/1.4895205
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2. Effect of Water Content on Partial Ternary Phase Diagram
Water-in-diesel Microemulsion Fuel
Hastinatun Mukayata
, Khairiah Haji Badria,b
, Ismail Ab. Ramanc
, Suria Ramlia,b
a
School of Chemical Sciences and Food Technology, Faculty of Science and Technology
Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia
b
Polymer Research Center, Faculty of Science and Technology, Universiti Kebangsaan Malaysia,
43600 UKM Bangi, Selangor, Malaysia
c
Advanced Oleochemical Technology Division (AOTD), Malaysian Palm Oil Board (MPOB)
6, Persiaran Institut, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
Abstract. Introduction of water in the fuel gave a significant effect to the reduction of pollutant such as NOx emission. In
this work, water/diesel microemulsion fuels were prepared using compositional method by mixing water and diesel in the
presence of non-ionic surfactant and co-surfactant. The effects of water composition on the partial ternary phase diagram
were studied at 5%, 10%, 15% and 20% (w/w). The physical stability of the microemulsion was investigated at 45°C over
a period of one month. The optimum formulae obtained were diesel/T80/1-penthanol/water 60:20:15:5 wt% (System 1),
55:20:15:10 wt% (System 2), 50:20:15:15 wt% (System 3) and 45:20:15:20 wt% (System 4). Physicochemical
characterizations of optimum formulae were studied. The results showed that water content has a significant effect to the
formation of microemulsion, its stability, droplet size and viscosity.
Keywords: fuel, partial ternary phase diagram, pollutant, water/diesel microemulsion
PACS: 80
INTRODUCTION
Due to the environmental and health concern, more stringent regulation on exhaust emission has been
implemented. United States have implemented much more stringent engine exhaust emission levels in The Clean
Air Act of 1990. Nitrogen oxide (NOx) is one of the pollutants which have been heavily monitored by the EPA. NOx
facilitates the formation of ozone in the air, results in the increasing level of ozone that can cause respiratory
ailments. Thus, provide a strong encouragement to the search for alternative fuels [1].
Among various alternative fuels, introduction of water into diesel engine has a number of benefits. Water has
influence on reducing the peak flame temperature and lead to the reduction of NOx emission [2-4]. The presences of
water may assist in fuel atomization due to microexplosion, which occur during the evaporation of the water inside
droplets of fuel. These phenomenon lead to the complete combustion and hence improve the combustion efficiency
[2-4]. There is also considerable evidence that introduction of water into diesel can helps reduction in the particulate
matter emission [4]. Most important aspect is that diesel emulsions can be used without engine modifications [5].
There are three techniques of introducing water into diesel engines which are injection of water into cylinder
using a separate injector, spraying water into inlet air and water-diesel emulsion. Among these three methods, it has
been concluded that water-diesel emulsion was the most effective way for the reduction of diesel particulate, for
four strokes DI engine [4]. Typically, introduction of water in the fuel is in the range of 10 to 20% [5]. Although
water-diesel emulsion was the most effective, but this system of emulsion is thermodynamically unstable and easily
separates [2, 4]. To overcome these problems, the microemulsion technique has been proposed [4]. The terms
“microemulsion” and “emulsion” seem to imply the similarities between them; just differ in droplet size, but it is
not. Microemulsions are defined as transparent, thermodynamically stable colloidal dispersions of oil and water
stabilized by a surfactant and/or co-surfactant. The diameter of the dispersed-phase droplet is less than one-fourth
the wavelength of the visible light which is the reason for their transparency [6, 7] and microemulsion is low in
viscosity which make it more profitable than emulsion [8].
The 2014 UKM FST Postgraduate Colloquium
AIP Conf. Proc. 1614, 256-262 (2014); doi: 10.1063/1.4895205
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3. Very few studies of water-in-diesel microemulsion fuels have been reported in the literature. To date, only the
properties (e.g: viscosity, particle size), engine performance and emission of microemulsion fuels have been
reported. Therefore, the main objective of the present work is to investigate the effect of water content on the partial
ternary phase diagram of water-diesel microemulsion fuel and their physicochemical properties. The percentage of
water content in the system was varied from 5% to 20%.
MATERIALS AND METHOD
Materials
Commercial diesel was purchased from local petrol station (kinematic viscosity, η =3.6095 mm2
/s, energy value,
H = 45.8 MJ/kg). The non-ionic surfactant, polyoxyethylene sorbitan monooleate (T80) with hydrophile-lipophile
balance (HLB) value of ~15.0 was supplied by Merck (M) Sdn Bhd. Selangor, Malaysia. The co-surfactant used was
1-penthanol and was manufactured by Fluka Sdn. Bhd. Distilled water was used to obtain the microemulsion
systems.
Method
The preparation of microemulsions was adopted from a published procedure applying constant composition
method [9]. The components used were T80, 1-penthanol and water + oil phase (W + O) with total mass of 10 g in a
screwed cap test tube. Composition of T80 and 1-penthanol were varied from 5 to 50% with 5% interval. The
portion of water in the system was varied from 5, 10, 15 and 20%. These mixtures were mixed by vortex and left for
1 to 2 days at ambient condition. The same mixture undergone microemulsion stability study at 45°C and was
observed for a month. These formulated microemulsions were qualitatively analyzed using polarized light sheets to
distinguish isotropic from anisotropic phases. The phases observed were constructed as partial ternary phase
diagrams according to Broze [9]. Each vertex of the triangular diagram represents 100% of that particular
component (or mixture of two components) and any point inside the triangular represents a ternary blend of each
basic component (water, oil, surfactant and co-surfactant) and can be read by drawing parallels to the three sides
from the selected point. Based on the partial ternary phase diagram, only those that fallen in the microemulsion
region would be selected. The selected microemulsions were characterized for droplet size and viscosity.
The droplet size of the selected microemulsions was determined by dynamic light scattering (DLS) (Zetasizer
Nano-ZS 90, Malvern, UK) technique conducted at 45°C. The refractive index of each sample was determined prior
to droplet size determination.
The kinematic viscosity of the selected microemulsions was determined using viscosity analyzer model HVM
472 Herzog at 40°C.
RESULTS AND DISCUSSION
Partial Ternary Phase Diagram of Diesel/Non-ionic Surfactant/Co-surfactant /Water
A ternary phase diagram was used to record the changes in composition and temperature for the three
components system and four components system. In this work, partial ternary phase behavior studies were carried
out on the diesel/T80/1-penthanol/water mixtures, and the phase diagrams were constructed based on data obtained
at 25°C and 45°C. FIGURE 1 to FIGURE 4 shows a partial ternary phase diagram of diesel/T80/1-penthanol/water
with water content of 5%, 10%, 15% and 20%, respectively.
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4. (a) (b)
FIGURE 1. Effect of 5% (w/w) water composition on ternary phase diagram of diesel/T80/1-penthanol/water at (a) 25°C and (b)
45°C.
(a) (b)
FIGURE 2. Effect of 10% (w/w) water composition on ternary phase diagram of diesel/T80/1-penthanol/water at (a) 25°C and
(b) 45°C.
microemulsion microemulsion
microemulsionmicroemulsion
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5. (a) (b)
FIGURE 3. Effect of 15% (w/w) water composition on ternary phase diagram of diesel/T80/1-penthanol/water at (a) 25°C and
(b) 45°C.
(a) (b)
microemulsionmicroemulsion
microemulsionmicroemulsion
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6. FIGURE 4. Effect of 20% (w/w) water composition on ternary phase diagram of diesel/T80/1-penthanol/water at (a) 25°C and
(b) 45°C.
These figures (FIGURE 1 to 4) indicated that as the water content increased, the region of microemulsion
decreased. Formation of microemulsion started at 10% (w/w) concentration of surfactant in the system that
contained 5% (w/w) water (FIGURE 1). On the other hand, the formation of microemulsion started at 20% (w/w)
concentration of surfactant with water composition of 20% (w/) (FIGURE 4). The formation of microemulsion
depends much on the composition of the surfactant and its solubility in the oil and water mixture. At lower water
level, less surfactant was required to reduce the interfacial tension. This promoted the formation of microemulsion
[10].
Effect of Water Composition on Stability of the Microemulsion
Stability of the microemulsion system was studied via clarity, phase separation and particle size determination
under different storage condition at 45 °C over a period of one month. FIGURE 1 to FIGURE 4 part (ii) showed that
the region of microemulsion decreased as water composition in the system increased. Upon increment in the volume
of dispersed phase led to an increase in the rate of coalescence. These resulted in increasing droplet size but
reduction in thickness of the interfacial film [11-12]. Tendency of the system to be instable was at risk due to limited
amount of surfactants [11]. The optimum composition was identified at concentration of surfactant and co-surfactant
at 20% (w/w) and 15% (w/w), respectively. At these points a clear single phase microemulsion was obtained which
was still stable over a month period. These parameters were used to prepare System 1, System 2, System 3 and
System 4 with water content of 5, 10, 15 and 20% (w/w), respectively. The systems were then analyzed.
Effect of Water Composition on the Droplet Size of Microemulsion
The effect of water composition on the droplet size of microemulsion was examined through graphical plot of
average droplet size (nm) against time (day) as shown in FIGURE 5. The droplet size was determined on day 0, 1, 3,
7, 14 and 30 at 45°C.
Time (day)
0 5 10 15 20 25 30 35
Averageparticlesize(nm)
60
70
80
90
100
110
120
130
System 4
System 3
System 2
System 1
FIGURE 5. Droplet size for each of microemulsion systems at 45°C.
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7. System 2, 3 and 4, followed a general trend of droplet size. The droplet size increased as the concentration of
dispersed phase increased [11-12]. Increased in volume fraction of dispersed phase cause an increase in interdroplets
attractive attraction thus increase the size of the droplets [13]. System 4 comprised of the highest water composition
has the largest size of droplet compared to other systems. Peng et al [11] has reported that droplet size was
influenced by the concentration of water in the system [11]. The droplet size of System 1 showed larger size despite
having less dispersed phase. The droplet size of microemulsion for these 4 systems was gradually increases over a
period of one month at storage condition 45°C due to an increase in the rate of coalescence [12].
Effect of Water Composition on the Viscosity of Microemulsion
The viscosity measurement for the systems was run and the result was compared with commercial diesel fuel
(TABLE (1)).
TABLE (1). Kinematic viscosity of water/diesel microemulsion fuel.
Sample
Kinematic viscosity,
mm2
/s
Conventional diesel 3.61
System 1 10.37
System 2 12.88
System 3 16.31
System 4 17.90
TABLE (1) indicated that all the systems have higher viscosity than commercial diesel fuel due to the
introduction of water in the systems. The kinematic viscosity for System 1, 2, 3 and 4 were 10.37 mm2
/s, 12.88
mm2
/s, 16.31 mm2
/s and 17.90 mm2
/s, respectively. As the volume of dispersed phase increased, the viscosity of the
microemulsion fuel also increased [14]. This might be due to the increasing of dispersed droplet number and size in
the system [15]. When the number of dispersed droplets increased, the attractive interaction of interdorplets also
increase and led the increment in viscosity [16].
CONCLUSION
Several phase diagrams of water/diesel microemulsion have been successfully constructed. Properties of
water/diesel microemulsion affected by water concentration were evaluated. Optimum systems obtained were
comprised of diesel/T80/1-penthanol/water 60:20:15:5 (wt%) (System 1), 55:20:15:10 (wt%) (System 2),
50:20:15:15 (wt%) (System 3) and 45:20:15:20 (wt%) (System 4) and found to be stable over one month storage
period. Water composition has a significant effect to the formation of microemulsion, its stability, droplet size and
viscosity. Thus, these preliminary findings can be used further on engine performance test and gaseous emission in
evaluating its potential as an alternative fuel.
ACKNOWLEDGMENTS
This study has been conducted mainly at Malaysian Palm Oil Board (MPOB) with the financial support of
Universiti Kebangsaan Malaysia (UKM) under the grant no GGPM-2012-109.
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