Egyptian Journal of Petroleum: S.T. Keera, S.M. El Sabagh, A.R. Taman
Egyptian Journal of Petroleum: S.T. Keera, S.M. El Sabagh, A.R. Taman
Egyptian Journal of Petroleum: S.T. Keera, S.M. El Sabagh, A.R. Taman
a r t i c l e i n f o a b s t r a c t
Article history: Biodiesel is evolving to be one of the most employed biofuels for partial replacement of petroleum based
Received 20 November 2017 diesel fuel, especially in recent years. The most widely used feedstocks for biodiesel production are
Revised 7 February 2018 vegetable oils. In this work, biodiesel production from castor oil has been synthesized by homogenous
Accepted 22 February 2018
alkaline transesterification. The influence of catalyst concentration, methanol:oil molar ratio, reaction
Available online 7 May 2018
temperature and reaction time in the methyl ester content reached by castor oil transesterification have
been evaluated. A yield of 95 wt% biodiesel was achieved at 1 wt% KOH, 60 °C, 9:1 methanol:oil ratio and
Keywords:
30 min reaction time. Transesterification at temperature 30 °C gave a yield compatibles with that
Biodiesel fuel
Castor oil
obtained at 60 °C. The composition of the fatty acid methyl ester was determined by Gas
Transesterification Chromatography. The castor oil biodiesel produced was blended with different concentrations of petro-
Gas chromatography diesel to obtain B5, B10 and B20. The biodiesel properties and its blends were determined according to
Biodiesel properties the standard test methods of analysis. The results showed that Castor oil biodiesel in the blends could
lower the cloud point value, but simultaneously, increases the viscosity of the diesel–biodiesel blends.
Thus, castor oil biodiesel with its very low cloud and pour points is suitable for using in extreme winter
temperatures.
Ó 2018 Egyptian Petroleum Research Institute. Production and hosting by Elsevier B.V. This is an open
access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction The most widely used feedstocks for biodiesel production are
vegetable oils. Among them, castor oil has two interesting
The depletion of the petroleum reserves, high oil prices and to phenomena as biodiesel raw material; on one hand, it does not
limit greenhouse gas emissions make renewable energy sources compete with edible oils; on the other, its cultivation does not
more attractive [1]. One of the best ways to reduce our dependence need high inputs [8].
on petroleum reserves is to develop renewable fuels such as bio- Castor oil extracts from the seeds, usually contain 40–55% of oil,
diesel [2]. a very high potential as compared to most other commonly used
Biodiesel is receiving international attention because of its fuel oil crops (soybean: 15–20% (w/w), sunflower: 25–35% (w/w),
properties and compatibility [3]. It has better properties than that rapeseed: 38–46% (w/w), and palm: 30–60% (w/w) [9]. In addition,
of petrodiesel such as renewable, higher biodegradability than the cost of cultivation can be 50% of the cost of cultivation rapeseed
fossil fuels, non-toxic, excellent lubricity and essentially free of and 25% of the cost of cultivation jatropha. In addition, because
sulphur and aromatics. Biodiesel fuel has the potential to reduce castor bean is not suitable for human consumption, its use as
the level of pollutants and probable carcinogens [4]. It is an envi- energy source does not compete with food production.
ronmentally friendly fuel that can be used in any diesel engine Castor oil contains 80–90% of hydroxyl fatty acid, ricinoleic acid
without the need to redesign the current technology [5]. It has bet- (Scheme 1) and about10% non-hydroxylated fatty acids, mainly
ter quality exhaust gas emission since the organic carbon present oleic and linoleic acids. Such especial composition causes a disad-
in it is photosynthetic in origin. It does not contribute to increase vantage for its use for biodiesel production, since its viscosity is
the level of carbon dioxide in the atmosphere and consequently about 7 times higher than the one of other vegetable oils [10]. To
to the greenhouse effect [6]. In spite of higher emission level of avoid this disadvantage, castor oil biodiesel when blends with pet-
NOx, the emission from biodiesel combustion contained lower rodiesel it has achieved effective specifications in standards [11].
amounts of CO, CO2, HC and smoke [7]. The presence of the hydroxyl group (–OH) attached to the hydro-
carbon chain in ricinoleic acid of the castor oil molecule makes
castor oil chemically quite different from the other oils; especially
Peer review under responsibility of Egyptian Petroleum Research Institute.
its elevated viscosity and polarity render it extremely valuable for
⇑ Corresponding author.
the industrial production of coatings, plastics and cosmetics [12].
E-mail address: keerasafaa@yahoo.com (S.T. Keera).
https://doi.org/10.1016/j.ejpe.2018.02.007
1110-0621/Ó 2018 Egyptian Petroleum Research Institute. Production and hosting by Elsevier B.V.
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
980 S.T. Keera et al. / Egyptian Journal of Petroleum 27 (2018) 979–984
3.1.3. Effect of temperature Fig. 3. Yield of methyl ester at different temperatures (30 & 60 °C) as a function of
Reaction temperature is another important criterion that will time, 9:1 methanol:oil molar ratio and 1 wt% catalyst concentration.
affect the yield of biodiesel. An experiment was run at the optimal
condition, 1 wt% catalyst, 9:1 methanol:oil molar ratio, reaction
time (30–120 min) and temperature 30 °C as shown in Fig. 3. It is acid and methanol, providing an elevated miscibility of castor oil in
illustrated that, the steady state of the reaction is reached within this alcohol. This happened due to the high miscibility of castor oil
a short period of time (30 min) because of the polarity of ricinoleic in methanol at room temperature. But after 30 min of the reaction
this variable is not somewhat important. It is clear that the ester
yield between 30 °C and 60 °C changes by only 2% wt. Hence the
reaction to be occurs at 30 °C is very suitable.
Table 1
Composition of biodiesel obtained by castor oil transesterification using GC.
Table 2
Physico-chemical properties of COME (B100) and Petrodiesel (B0) blends.
obtained are very much consistent with those reported in other fluid motion. Viscosity is the major reason why fats and oils are
research workers [44]. Just like other vegetable oils, castor oil is a transesterified to biodiesel. The viscosity of biodiesel is approxi-
triglyceride of various fatty acids and about 10% glycerin. The fatty mately an order of magnitude lower than that of the starting oil
acids consist of approximately 80–90% ricinoleic acid, 3–6% linoleic or fat. Table 2 shows that castor oil has a high viscosity (231.22
acid, 2–4% oleic acid and 1-5.5 saturated fatty acids. The high con- cSt at 40 °C). As a result, biodiesel produced from castor oil
tent of ricinoleic acid is the reason for the versatility of castor oil (B100) has extremely high viscosity value (15.40 cSt) exceeding
in technology [45,46]. Fig. 4 presents a typical chromatogram for by far the international standard limit. This has been attributed
the COME. One can see the formation of a major peak of methyl ester to the presence of OH groups in ricinoleic acid tend to form hydro-
that referrers to methyl ricinoleate, which the result of methanolysis gen bonds with other hydrogen atoms present in other molecules
of ricinoleic acid, the main component of castor oil. [16]. Consequently, it can be suggested to mix this COME with pet-
rodiesel in different proportions in order to reach the viscosity
3.3. Physico-chemical characterization of the COME and its blends specification. The lower the viscosity of the oil, the easier it is to
pump and atomize and achieve finer droplets. It is evident from
Six different volumes based blends were prepared from Diesel: Table 2 that there is an increase in viscosity with corresponding
COME mixtures [100:0 (B0), 95:5(B5), 90:10(B10), 80:20(B20) and increase in COME percentage in the blends. B5, B10 and B20 give
0:100(B100]. Properties of the blends were subjected to evaluation the viscosity values 2.66, 3.14 and 3.73 cSt respectively, which
according to standard test methods of analysis and were tabulated within the accepted standard range of viscosity. So COME treated
in Table 2. with petrodiesel oil will has better injection characteristics.
COME is a consequence of the presence of the hydroxyl group of high (0.15%) meanwhile that of petrodiesel is 0.02%. Water in the
the ricinoleic acid methyl ester. COME can be mixed with diesel biodiesel can promote microbial growth, lead to tank corrosion,
up to 20% without exceeding the standard accepted ratio for participate in the formation of emulsions, as well as cause
biodiesel density. The density improved with decreasing COME hydrolysis or hydrolytic oxidation. Hence to overcome such issues,
concentration in the blend. From Table 2, the respective values its blend with diesel has proven effective up 20% to comply with
for B20, B10 and B5 present 0.8595, 0.8491 and 0.8435 specifications in standards.
respectively.
3.3.8. Total acid number
3.3.3. Cloud point and pour point The data (Table 2) reveal that 1.19 mg KOH/g is the total acid
The two important parameters for low temperature applica- number of castor oil. COME has 0.63 mg KOH/g which exceeds that
tions of a fuel are cloud point (CP) and pour point (PP). The CP is of diesel (0.12 mg KOH/g). Blend with concentration up to 20%
the temperature at which wax first becomes visible when the fuel COME could be acceptable. The total acid number decreases almost
is cooled. The PP is the temperature at which the amount of wax linearly with decreasing percentage of biodiesel in the blend and
out of solution is sufficient to gel the fuel, thus it is the lowest tem- B5 gives the best value (0.15 mg KOH/g).
perature at which the fuel can flow.
It is generally known that biodiesel has higher CP and PP com-
pared to conventional Diesel, meanwhile methyl esters of castor oil 3.3.9. Cetane number
has a very low cloud and pour points which make this biofuel con- CN is a measure of biodiesel ignition quality, which decreases
sidered to be a good alternative in winter conditions. So a blend of with decreasing chain length and increasing branching and unsat-
COME with petrodiesel (Table 2) shows good flow properties and uration. It is a measure of the fuel ignition delay, higher CN value
the properties improved with increasing COME concentration in indicating shorter time between initiation of fuel injection and
the blend. B5, B10 and B20 give, cloud point -3, -6, -9 and pour ignition. Table 2 present cetane number of petrodiesel is 51. Cetane
point -9, -12,-18 respectively. It indicates that castor oil biodiesel number of COME is lower, regarding to the consequence of the
also could be used as petroleum diesel additive for improving cold presence of the free hydroxyl group of castor oil molecule, besides
flow properties. the presence of the double bonds of the ricinoleic acid. Cetane
number of COME gives 43.7. This value is lower than that of stan-
3.3.4. Sulphur content dard. A possible solution to meet the standard 47 is the blending
It is clear that castor oil is sulphur free (Table 2). Consequently with petrodiesel. The results show that, B5, B10 and B20 give
COME (B100) is sulphur free. This is one of the major advantages of 50.6, 49.1 and 48.8 cetane numbers respectively.
this biodiesel. Blend of COME with petrodiesel shows a decrease in
sulphur content with increasing COME in the blend from B5 to B20 4. Conclusion
(0. 15–0. 01 wt%), while that of petrodiesel is 0.85 wt%. This low
sulphur has advantages both for the environment and the engine - Castor oil biodiesel fuel properties are within the recommended
life. Low sulphur is required to reduce exhaust emissions. standards of biodiesel fuel except the viscosity.
- Biodiesel obtained from castor oil has a very low cloud and pour
3.3.5. Flash point points which makes this biodiesel a good alternative in winter
Flash point is the temperature at which the fuel can ignite when conditions.
exposed to a heat source. It is important from the point of view of - Castor oil biodiesel could be used as petroleum diesel additive
safe handling, storage and transportation. It is known that high for improving both environmental and flow behavior of the
flash point ensures more safety in the handling and storage. It is mineral fuel.
clear from Table 2 that Castor Oil has its value 228 °C and after - Castor oil biodiesel has a lower cetane number value (43.7)
transesterification it is 194 °C which higher than that of diesel compared to petrodiesel (51).
(69 °C) and so why safe to store. It is noticed that the flash point - The blend B5 (biodiesel 5% to petrodiesel 95%) gave the best
increases with increase COME in the blend from, 79, 85.9 and cetane number value (50.6).
89.1 °C for B5, B10 and B20 respectively. Hence castor oil biodiesel
blend can be used as a flash point enhancing additive and can be
classified as a non-hazardous fuel.
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