physicochemical characterization and thermal behavior of biodiesel and biodiesel–diesel blends.pdf

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Physicochemical characterization and thermal behavior of biodiesel and

biodiesel–diesel blends derived from crude Moringa peregrina seed oil

Mohammed Salaheldeen a,b,⇑, M.K. Aroua a, A.A. Mariod c,d, Sit Foon Cheng e, Malik A. Abdelrahman b,f ,A.E. Atabani g,h

a Chemical Engineering Department, Faculty of Engineering, University Malaya, 50603 Kuala Lumpur, Malaysiab Department of Chemistry, Faculty of Science, Sudan University of Science and Technology, P.O. Box 407, Khartoum, Sudanc College of Sciences and Arts-Alkamil, King Abdulaziz University, Alkamil, Saudi Arabiad Department of Food Science & Technology, College of Agricultural Science, Sudan University of Science and Technology, P.O. Box 407, Khartoum, Sudane Unit of Research on Lipids, Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia

f Department of Chemistry, College of Medical Science (Turuba), Taif University, Saudi Arabiag Department of Mechanical Engineering, Faculty of Engineering, Erciyes University, 38039 Kayseri, Turkeyh Erciyes Teknopark A.S , Yeni Mahalle Asıkveysel Bulvarı Erciyes Teknopark, Tekno 3 Binası 2, Kat No: 28, 38039 Melikgazi/Kayseri, Turkey

a r t i c l e i n f o

Article history:

Received 23 July 2014

Accepted 29 December 2014

Available online 21 January 2015

Keywords:

Moringa peregrina

Biodiesel

Fuel properties

Thermal stability

a b s t r a c t

Moringaceae is a monogeneric family with a single genus i.e. Moringa. This family includes 13 species. All

these species are known as medicinal, nutritional and water purification agents. This study reports, for

the first time, on characterization of the biodiesel derived from crude Moringa peregrina seed oil and

its blends with diesel. The crude oil was converted to biodiesel by the transesterification reaction, cata-

lyzed by potassiumhydroxide. High ester content (97.79%) was obtained. M. peregrina biodiesel exhibited

high oxidative stability (24.48 h). Moreover, the major fuel properties of M. peregrina biodiesel conformed

to the ASTM D6751 standards. However, kinematic viscosity (4.6758 mm2/s), density (876.2 kg/m3) and

flash point (156.5 C) were found higher than that of diesel fuel. In addition, the calorific value of M. per-

egrina biodiesel (40.119 MJ/kg) was lower than the diesel fuel. The fuel properties of M. peregrina biodie-

sel were enhanced significantly by blending with diesel fuel. In conclusion, M. peregrina is a suitable

feedstock for sustainable production of biodiesel only blended up to 20% with diesel fuel, considering

the edibility of all other parts of this tree.

2015 Elsevier Ltd. All rights reserved.

1. Introduction

Fossil fuels reservoirs around the world are declining due to

their non-renewable nature. At the same time the demand for

energy is, continuously, increasing to meet the needs of the world

population, which is growing significantly. As a result, the prices of

fossil fuels have increased and, negatively, affected the economies

of many countries. Global warming is being caused by the green-house gas emissions. Reducing the dependence on fossil fuels will

be beneficial, from environmental point of view, since this will

reduce the concentration of carbon dioxide in the atmosphere.

Therefore, explorations to find new renewable, sustainable and

economically feasible sources of energy have emerged as a top pri-

ority for research to resolve all these problems.

Biodiesel is one of the most promising alternative fuels to

replace the conventional petroleum-based fuels with multiple

environmental advantages. Biodiesel, popularized as the mono

alkyl esters are derived from triglycerides (vegetable oils or animal

fats). Transesterification is the most convenient process to convert

triglycerides to biodiesel. Transesterification process involves areaction of the triglyceride feedstock with light alcohol in the

presence of a catalyst to yield a mixture of mono alkyl esters [1].

Currently, homogenous basic catalysis, using hydroxides of sodium

or potassium, is the common route for industrial production of

biodiesel [2].

Biodiesel industry has grown up in the world using edible

feedstock such as rape seed, soybean, sunflower and palm oils.

Non-edible oils stand as new promising sources of raw materials

for biodiesel production, especially in developing countries to

satisfy their increasing energy demand [3]. Currently, Jatropha

curcas has been promoted as the most promising non-edible source

http://dx.doi.org/10.1016/j.enconman.2014.12.087

0196-8904/ 2015 Elsevier Ltd. All rights reserved.

⇑ Corresponding author at: Department of Chemistry, Faculty of Education, Nile

Valley University, P.O. Box 347, Atbra, Sudan. Tel.: +249 122718984.

E-mail addresses: [email protected] (M. Salaheldeen), [email protected].

my (M.K. Aroua), [email protected] (A.A. Mariod), [email protected]

(S.F. Cheng), [email protected] (M.A. Abdelrahman), [email protected]

(A.E. Atabani).

Energy Conversion and Management 92 (2015) 535–542

Contents lists available at ScienceDirect

Energy Conversion and Management

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / e n c o n m a n

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for bio-fuel [4]. However, all parts of Jatropha are toxic [5]. There-

fore, plantation of such toxic plant for large scale and long term

production may raise risks, such as accidental consumption by

children or animals. Moreover, the situation is being worsened

by spreading Jatropha on the fertile lands in order to improve the

yields, as this will reduce water and available space for food crops

[6]. Thus, plants that can supply, simultaneously, food and fuel

should be given more attention as robust feedstock for bio-fuels.

In this respect, Moringa seed oil has emerged as a potential feed-

stock for biodiesel production, considering the one hundred per-

cent usability of all other parts of this tree [7]. All nutritional

values and medicinal usage of Moringa have been comprehensively

reported [8]. After oil extraction from the seeds, the residues

remain are potential for both water purification and as a fodder [9].

Moringa is a single genus of the Moringaceae family. This family

includes 13 species. All these species originated in India and Africa

and have been distributed in many other several tropics lately [10].

Moringa oleifera [11–13] and Moringa stenopetala [14] have been

reported for biodiesel production. Preliminary study [15] revealed

that crude M. peregrina seed oil is potential for biodiesel produc-

tion. M. peregrina oil has high degree of unsaturation, comprised

of oleic acid as a major component [16]. Thus, other preliminary

studies [17,18], indicated the potential of M. peregrina oil for edible

purposes and other industrial application, such as hydrogenation,

shortening production and others.

M. peregrina is distributed in wide range extending from Egypt,

Ethiopia to Somalia, Sudan, the Red Sea region, Palestine and

Jordan [19]. M. peregrina as it is very fast growing tree, can reach

3–10 m in height during only 10 months from the plantation of

the seed. It has grayish–green bark, long leaves, and bisexual

yellowish white to pink, showy, fragrant flowers. The fruits are

elongate capsules, with a beak, glabrous and slightly narrowed

between the seeds. The seeds are globose to ovoid or trigonous

[10,19,20]. Plantations of M. peregrina have been assessed as quite

promising, with growth reasonably rapid and cultivation easy [15].

The aim of this study is to investigate the properties of

M. Peregrina biodiesel for the first time. The oil was extracted fromM. peregrina seeds. The extracted crude oil was converted to

biodiesel by the transesterification reaction in one step, catalyzed

by potassium hydroxide. The produced biodiesel was blended with

diesel fuel No. 2. Physical characteristics of the biodiesel and bio-

diesel–diesel blends were discussed in the light of the international

standards ASTM (American Society for Testing and Materials) D

6751. The ester content in the produced biodiesel was determined

and discussed in accordance to the European Standards EN14214

using the method EN14103.

2. Experimental

2.1. Materials

M. peregrina seeds were purchased from the Forest National

Corporation of the River Nile State in Sudan. The seeds were

cleaned to remove damaged seeds, sand, stones, wood and any

other foreign materials. The cleaned seeds were packed in plastic

bags and stored in a cold room until extraction. Diesel No. 2 was

purchased from a local petroleum station in Kuala Lumpur in

Malaysia, near University of Malaya. Pure analytical standards of

fatty acid methyl esters (FAME), a mixture of (C4–C24) and pure

methyl heptadecanoate were purchased from Sigma–Aldrich

(Malaysia). All other reagent, like n-hexane 95%, sodium sulfate

anhydrous, potassium hydroxide, phenolphthalein indicator, etha-

nol 95%, and methanol 99.9%, were analytical grade and were pur-

chased from Merck (Malaysia). All reagents and standards wereused as received without any further drying or purification.

2.2. Oil extraction

M. peregrina seeds were crushed by grinder and sieved to less

than 1 mm in size. The meal (500 g) was placed in a soxhlet extrac-

tor. A cotton cloth was used as a thimble to hold the sample. The

extractor was fitted with round bottom flask (5 L) and a condenser.

The extraction was carried out using hexane (3 L). After 6 h extrac-

tion time, the solvent was recovered by rotary evaporator at 40 C

under vacuum. The oil was dried with sodium sulfate anhydrous

prior to biodiesel production.

2.3. Biodiesel production

The average acid value of the extracted M. peregrina seed oil was

found (0.68 mg KOH/g). It was, early, reported that the acid value

below 1.0 mg KOH/g oil, render the conversion of the vegetable

oil to biodiesel feasible by a one step base-catalyzed transesterifi-

cation reaction without significant mass loss due to saponification

[21]. The reaction was carried out in a batch reactor, which consists

of a glass jacket reactor (2 L) equipped with condenser and water

bath to control the temperature. 0.600 L of the oil were placed in

the reactor and warmed to 60 C. Simultaneously, fresh methanolic

potassium hydroxide was prepared by mixing 5.267 g potassium

hydroxide in 0.150 L pure methanol. The resultant solution was

poured into the reactor after the temperature established at

60 C. The amounts of the components of the reaction mixture

were chosen to afford 6:1 methanol/oil molar ratio and 1% (w/w)

of oil catalyst. The reaction was allowed to run under continuous

stirring for two hours. At the end, the reaction mixture was trans-

ferred to a separated funnel where two distinct layers were formed

by standing (12 h). The lower layer contained glycerol and the

upper layer contained the methyl ester of the oil. The lower layer

was drained and the layer of the biodiesel was washed gently with

warm water until the drained washing became neutral, to remove

the soaps, methanol, residual glycerol and the other impurities.

The residual methanol and water were removed by the means of

a rotary evaporator. Finally, the biodiesel was further dried withsodium sulfate anhydrous to remove the traces of water.

2.4. Infrared spectroscopy

The conversion of the vegetable oil to biodiesel was investigated

by Fourier transform infrared spectroscopy (FTIR). Bruker tensor 27

FT-IR spectrophotometer (Germany), equipped with attenuated

total reflectance (ATR) cell that has a ZnSe single crystal, was used

to obtain the IR spectra (absorbance mode) in the region 400–

700 cm1 with 24 scans and 41 resolution.

2.5. Ester content and fatty acid composition determination

Gas chromatography (GC Shimadzu 2010, Japan) was used toanalyze the fatty acid composition of the produced biodiesel. The

operating conditions are shown in Table 1. The retention times of

the methyl esters of the sample were compared to those of the

standard FAMEs. Quantity of each component was calculated from

the relative peak area and considered as a percentage by mass. The

ester content in the sample of biodiesel was determined according

to the EN14103 method [22], using methyl heptadecanoate as an

internal standard. All the values are reported as a mean of dupli-

cate determination.

2.6. Biodiesel–diesel blending

Biodiesel–diesel blends were prepared at ambient temperature

in glass bottles and homogenized by agitation (2000 rpm) for30 min. Six blends (5%, 10%, 20%, 40%, 60% and 80% v/v) were

536 M. Salaheldeen et al. / Energy Conversion and Management 92 (2015) 535–542


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prepared to investigate the effect of blending on biodiesel proper-

ties at low and high blend ratios.

2.7. Fuel properties determination

Some fuel properties of the crude oil, biodiesel and biodiesel–

diesel blends were examined according to ASTM D6751. These

properties include calorific value, kinematic viscosity, viscosity

index, density, cloud point (CP) pour point (PP), cold filter plugging

point (CFPP), flash point and oxidative stability. Table 2 shows thedescription of the equipment and their manufactures, along with

the ASTM methods that were used to conduct these analyses in this

study. The acid values of the crude M. peregrina oil and its biodiesel

were determined by titration according to Kuntom et al. [23].

Cetane number (CN) of biodiesel is directly proportional to the

length of the carbon chain and inversely to the number of the dou-

ble bonds. Therefore, it was calculated based on the iodine value

(IV) and Saponification number (SN) according to Eq. (1) as

reported by Krisnangkura [24]. IV and SN were calculated accord-

ing to Eqs. (2) and (3) respectively [25]:

CN ¼ 46:3 þ ð5458=SNÞ ð0:225 IVÞ ð1Þ

IV ¼X560 Ai D

MWi

ð2Þ

SN ¼X254 D Ai

MWið3Þ

where Ai, D and MWi stand for concentration by percentage, num-

ber of double bond and molecular weight of each methyl ester.

2.8. Thermal analysis

Volatility is one of the most important properties to determine

the viability of biodiesel as a fuel regarding engine performance. In

this study thermogravimetric analyzer TGAQ500 (TA instruments,

USA) was used to investigate the thermal behavior of M. peregrina

biodiesel and the effects of blending with diesel on its volatility.

The sample (5–8 mg) was heated from ambient temperature to

600 C with a heating rate 10 C/min in an inert atmosphere of

pure nitrogen at a flow rate of 100 ml/min. The obtained data were

analyzed using the universal analysis 2000 software.

3. Results and discussion

3.1. Crude oil properties

Extraction process revealed that M. Peregrina seed had an oilcontent 26% of dry base from the whole seed. The extracted oil

had very low free fatty acid content (0.34%), equivalent to

0.68 mg KOH/g oil, eliminating the need of acid pretreatment step

as explained in the experimental part (2.3). Table 3 shows some

properties of crude M. peregrina seed oil in comparison to some

common edible and non-edible vegetable oils [13] for biodiesel

production. The kinematic viscosity of crude M. peregrina seed oil

at 40 C was found 36.181 mm2/s, which is 11 times higher than

the viscosity of diesel fuel (3.1135 mm2/s) as reported in Table 5.

Moreover, crude M. peregrina seed oil was found to have high flash

point (268.5 C). Flash point is inversely proportional to the volatil-

ity of the vegetable oils [26]. Therefore, the transesterification

reaction is necessary to improve the viscosity and volatility of

crude M. peregrina seed oil.

3.2. Infrared spectra of M. peregrina seed oil and its biodiesel

The conversion of crude M. peregrina seed oil to methyl ester

and the purity of the produced biodiesel were examined by the

FTIR spectroscopy. Fig. 1 displays the FTIR spectra of the crude M.

peregrina seed oil and its methyl ester. A comparison between

the two spectra in the region of 1500–1000 cm1, showed a signif-

icant differences, which are attributed to the replacement of

CH2OA group in the triglyceride by the CH3OA group in the methyl

ester. A new peak, which does not exist in the spectra of the oil,

appeared in the spectra of the methyl ester at 1435.58 cm1 due

to the deformation vibration of the methoxy group (CH3OA). This

peak represents a direct indicator for the conversion of the oil to

methyl ester [27,28]. Another, significant, difference was observed

in the range 1300–1060 cm1 as a result of the esteric bond (C–O)

stretching vibration. In this range, the crude oil showed strong

broad peak at 1159.63 cm1 due to the absorbance of the triple

ester group in the triglycerides [28]. Whereas, the methyl ester

showed two peaks at 1195.64 cm1 and 1169.30 cm1. The new

peak at 1195.64 cm1 is explained by the presence of the methyl

group near the carbonyl group. The peak at 1244.47 in the spec-

trum of the methyl ester is assigned to the asymmetrical stretching

of the group C–O–C. The same group is noticed at 1236.47 cm1 in

the oil spectrum [29]. The absence of broad peak in the region

2500–3300 cm1 indicates the very low concentrations of impuri-

ties that contain hydroxyl groups such as water, methanol free

glycerol and free fatty acids [30]. Moreover, no peak was observed

in the region1650–1540cm1 indicating the absence of soap in the

Table 1

GC conditions for determination of fatty acid composition.

Property Specification

Injector Split 1:50 at 240 C and 1 lL injection volume

Column BPX70 (300.32mm ID and 0.25 mm film thickness)

Gas currier Hydrogen 64.4K Pa, total rate flow 59.9ml/min and

column flow is 1.1 ml/min

Detector FID at 260 C

Heating program 140 C hold 2 min, 8 C to 1653 C/min to 192

8 C/min to 220 holding 12 min

Table 2

List of the equipment used in the fuel properties determination.

Property Equipment Manufacturer Standard method

Kinematic viscosity SVM 3000-automatic Anton Paar, UK D 445

Viscosity index SVM 3000-automatic Anton Paar, UK D2270-04

Density SVM 3000-automatic Anton Paar, UK D 7042

Calorific value C2000 basiccalorimeter–automatic IKA, UK D 240

Cloud point (CP) Cloud and pour point tester – automatic NTE 450 Normalab, France D 2500

Pour point (PP) Cloud and pour point tester – automatic NTE 450 Normalab, France D97

Cold filter plugging point (CFPP) Cold filter plugging point – automatic NTL 450 Normalab, France D 6371

Oxidative stability (OS) 873 Rancimat – automatic Metrohm, Switzerland EN 14112

M. Salaheldeen et al./ Energy Conversion and Management 92 (2015) 535–542 537

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biodiesel [33], which indicates that the step of washing was satis-

factory. The whole FTIR spectrum of M. peregrina methyl ester

obtained for this study, is similar to the spectra that were recorded

for palm, soybean and sunflower methyl esters [30], indicating that

crude M. peregrina seed oil is a new feedstock potential for biodie-

sel production.

3.3. Ester content and composition of M. peregrina biodiesel

The yield of biodiesel was found 92.33% (v/v). The ester content

in the produced biodiesel was determined by the GC analysis

according to the EN14103 standard method. The average value of

the ester content, obtained from duplicate determination, was

97.79% with absolute difference 1.1%. EN14103 stated that theabsolute difference between two independent single test results

shall not be greater than 1.6%. Thus, the value obtained here is sat-

isfactory regarding repeatability. This value of the ester content

(97.79%) is greater than the minimum value required by the

EN14103 (96.5%). The glycerol portion of the original vegetable

oil is usually about 10.5%, thus, values of ester content greater than

97.7% indicates that the residual total glycerol is lower than the

maximum value (0.24%) required by the ASTM D6751 [31]. It is

concluded here from the GC analysis that the obtained M. peregrina

methyl ester had high purity.

The composition of M. peregrina methyl ester as identified from

the GC analysis is presented in Table 4. For the sake of comparison

between different species in the same family, Table 4 also includes

the fatty acid composition of methyl esters derived from M. oleifera[11] and M. stenopetala [13] oils. The prominent feature of all these

species is the presence of oleate fatty ester as the dominant com-

ponent (71–76%) and very low content (>5%) of polyunsaturated

fatty esters. Methyl esters that contain a high fraction of

Table 3

Physical properties of crude M. peregrina seed oil in comparison to some other oils.

Property M. peregrina this study M. oleifera [13] Palm [13] Soybean [13] Canola [13] Jatropha [13]

Kinematic viscosity at 40 C (mm2/s) 36.181 43.4680 41.932 35.706 35.706 48.095

Kinematic viscosity at 100 C (mm2/s) 7.9707 9.0256 8.4960 7.6295 8.5180 9.1039

Viscosity index (VI) 201.1 195.20 185.0 223.5 213.5 174.1

Density (kg/m3) 892.8 897.1 899.8 907.3 904.2 905.4

Flash point (C) 268.5 263 254.5 280.5 290.5 258.5

Calorific value (MJ/kg) 39.916 39.762 39.867 39.579 39.751 38.961Oxidative stability (h) 29.255 41.7 0.08 6.09 5.64 0.32

Fig. 1. (a) FTIR spectrum of crude M. peregrina seed oil and (b) FTIR spectrum of M. peregrina methyl ester.

Table 4

Fatty acid composition of M. peregrina methyl ester in comparison to M. oleifera

methyl ester and M. stenopetala methyl ester.

M. peregrina methyl

ester

M. oleifera methyl

esteraM. stenopetala methyl

esterb

C16:0 9.08 6.50 6.10

C16:1 2.68 – –

C18:0 4.04 4.40 7.50

C18:1 71.09 72.20 76.0

C18:2 4.16 1.00 –C18:3 0.51 –

C20:0 2.38 4.0 3.80

C20:1 1.86 2.00 1.70

C22:0 3.13 7.10 4.40

C24:0 1.02 – –

TUFEsc 80.30 75.20 77.70

TMFEsd 75.63 74.20 77.7

TPUFEse 4.66 1 –

TSFEsf 19.7 24.80 22.3

VLCFEsg 8.39 13.10 9.90

a Ref. [11].b Ref. [14].c Total unsaturated fatty esters.d Total monounsaturated fatty esters.e Total poly unsaturated fatty esters.f Total saturated fatty esters.

g Very long chain fatty esters.



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monounsaturated fatty esters are capable to balance between the

different fuel characteristics [32]. Therefore, Moringa seed oil is a

promising feedstock to produce biodiesel fuel with high quality.

3.4. Fuel properties of M. peregrina biodiesel

The major fuel properties of M. peregrina methyl ester were

determined and compared to the diesel fuel. These results areincluded in Table 5.

Acid value was reduced to very low concentration

(0.11 mg KOH/g) satisfying the ASTM standard maximum limits

(0.5 mg KOH/g).

Kinematic viscosity is related directly to the resistance of fluids

to flow. Thus, it is an important property to determine the effi-

ciency of a biodiesel as a fuel. High viscosity will reduce the quality

of the liquid fuel due to poor atomization, tubing blockage and pos-

sible deposits formation in the engine causing incomplete combus-

tion and severe fouling. As viscosity varies inversely with

temperature all these drawbacks increase at low temperature, so

fuels with high viscosities are not suitable for cold regions [33].

The effect of temperature change on the viscosity is indicated by

the viscosity index, which is an arbitrary number that can be calcu-lated from the viscosities at 40 and 100 C according to the ASTMD

2270-4 method. The effect of temperature change on the viscosity

is minor for fuels that have high viscosity index [34]. Kinematic

viscosity of M. peregrina methyl ester, for this study, was found

4.7658 mm2/s at 40 C, significantly lower than the Kinematic vis-

cosity of the apparent vegetable oil (36.181 mm2/s), indicating that

the transesterification reaction was efficient at the prescribed con-

ditions. This value falls in the range specified by ASTM standards

(1.9–6.0 mm2/s) and similar to the values obtained for biodiesel

fuels derived from M. oleifera (4.83 mm2/s) [11], M. stenopetala

(4.58 mm2/s) [14], J. curcas (4.723 mm2/s), palm (4.6889 mm2/s),

soybean (4.3745 mm2/s) and canola (4.5281) [13]. However, kine-

matic viscosity of M. peregrina methyl ester is still higher by 53.07%

than the diesel fuel (3.1135 mm

2

/s). M. peregrina methyl ester has,a relatively, high viscosity index (200.3) and falls in the range that

was observed for the methyl esters of Jatropha, palm and M. oleif-

era (194–207) and lower than the viscosity index of biodiesel that

were derived from canola (236.9) and soybean oils (257.8) [13].

The density of M. peregrina methyl ester at 15 C was found

(876.2 kg/m3), slightly greater than the density of the diesel fuel

(5%). Although the density of a fuel has less significant effect on

the engine performance compared to the viscosity [35] the, rela-

tively, higher density of biodiesel compared to diesel fuel will

increase the fuel consumption and consequently NOx emissions

[36]. Calorific value is another fuel property that affects fuel con-

sumption [33]. The calorific value of M. peregrina methyl ester

was 40.119 MJ/kg lower than the calorific value of the diesel fuel

(45.685 MJ/kg). The lower calorific value of biodiesel fuels because

of their oxygen content. However, the presence of oxygen in the

biodiesel leads to complete combustion of the fuel in the diesel

engine [36].

Cetane number of a fuel is inversely related to its ignition delay

i.e. the time between the initial fuel injection and ignition. There-

fore, alkyl esters with high cetane numbers are favorable for the

diesel ignition engine regarding ignition quality [36]. The value

of cetane number of M. peregrina methyl ester in this study was

found 56.42 higher than the minimum value (47) that is specified

by the ASTM standard. Generally, Cetane number of biodiesel var-

ies in the range (48–67) [37]. Therefore, M. peregrina methyl ester

can be considered among biodiesel fuels that has a high cetane

number, as another indication for the suitability and potentiality

of M. peregrina for biodiesel production.

As expected, due to the low concentration of the polyunsatu-

rated fatty esters (PUSFEs) (C18:2 and C18:3), M. peregrina methyl

ester has exhibited a high oxidative stability (24.48 h).This value is

similar to the value (26.2 h) reported for M. oleifera oil methyl ester

[12].

High flash point of biodiesel fuel is another advantage of biodie-

sel over petroleum-based diesel fuel. Flash point is a measure to

the flammability of the fuel, higher the flash point more safe the

fuel in handling and storage [13]. The flash point of the produced

biodiesel in this work was 156.5 C, quite satisfactory as the mini-

mum value of the flash point prescribed by the ASTM a standard is

120 C. However, high flash point indicates low volatility proper-

ties, leading to negative effect on diesel engine performance [32].

The volatility characteristics and thermal behavior of M. peregrina

methyl ester was further investigated by the thermogravimetric

analysis (discussed in the Section 3.6)

The behavior of biodiesel during cold seasons can be evaluated

from the cold flow properties which are cloud point (CP), pour

point (PP) and cold filter plugging point (CFPP). The CP is the tem-perature at which smallest lump of crystals become visible when

the fuel is cooled. The PP is the lowest temperature at which the

fuel flows though the formation of gel due to the effect of cooling.

The CFPP is the temperature at which the pores of the filter start to

plug by the effect of the crystallized components in the fuel [38]. In

this study M. peregrina methyl ester has shown, significantly, high

cold flow properties. CP, PP, and CFPP were found 15, 11, 13 C

respectively. This behavior can be explained by the considerable

concentration of saturated palmitic acid methyl ester C16:0

(9.08%) and the significant amount of very long fatty esters (VLC-

FEs) (8.39) [32]. The cold flow properties of the diesel fuel used

in this study were not low as expected and fall in the range similar

to the biodiesel under investigation. This may be an indication of

its high content of paraffin [39].

3.5. Fuel properties of biodiesel–diesel blends

As mentioned above, biodiesel investigated in this study was

observed with higher viscosity, density and lower volatility and

heating value compared to the diesel fuel. Blending biodiesel with

diesel fuel is beneficial from two points of view, to improve the fuel

properties of the biodiesel and to reduce the environmental pollu-

tion [40]. Six blends were prepared (5% (B5), 10% (B10), 20% (B20),

40% (B40), 60% B60) and 80% (B80) v/v) and were examined for

their physical properties compared to diesel fuel. The effect of die-

sel fuel on the fuel properties of the biodiesel is depicted in

Fig. 2(a–e). As expected the fuel properties of the M. peregrina

methyl ester were enhanced significantly as the fraction of the die-sel fuel increased in the blends. From Fig. 2(a), the blends of B5,

Table 5

Fuel properties of M. peregrina methyl ester in comparison to diesel fuel and ASTM D

6751 standard.

Property M. peregrina

methyl

ester

Diesel

fuel

ASTM D

6751

Acid value mg KOH/g 0.11 – 0.5 max

Kinematic viscosity at 40 C mm2/s 4.7658 3.1135 1.9–6.0

Viscosity index 200.3 165.5 –

Density at 15 C kg/m3 876.20 834.6 880

Iodine value mg I2/100 g 77.17 – –

Saponification number mg KOH/g 198.60 – –

Cetane number 56.42 – 47 min

Flash point C 156.5 – 120 min

Calorific value MJ/kg 40.119 45.685 –

Oxidative stability H 24.48 – 3 min

Cloud point (CP) C 15 13 –

Pour point (PP) C 11 11 –

Cold filter plugging point (CFPP) C 13 13 –


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B10, and B20 showed kinematic viscosities (3.173, 3.237,

3.371 mm2/cm, respectively) very close to the diesel fuel

(3.113 mm2/s). Fig. 2(b) shows, remarkable, reduction in the den-

sity of the biodiesel on increasing the ratio of the blends. The den-

sities of B5, B10 and B20 (836.4, 838.4, 842.7 kg/m3, respectively)

were so close to the density of the diesel fuel (836.4 kg/m3). As

illustrated in Fig. 2(c), the calorific value of the biodiesel was

increased, substantially, by increasing the diesel fuel proportion

in the blend due to the reduction of the oxygen content [41]. The

calorific values of B5, B10, B20 were (45.392, 45.110 and

44.517 MJ/kg, respectively) very close to the diesel fuel

(45.685 MJ/kg). As shown in the Fig. 2(d) significant reduction in

the flash point of the M. peregrina methyl ester was observed even

by a small proportion diesel fuel. Moreover, B5, B10, B20 had flash

points in the range 78–81 C so close to the flash point of the diesel

(77.5 C). Fuels with flash points higher than 66 C are believed to

be safe regarding hazardous flammability [41]. From Fig. 2(e) it

was, very, clear that the blending did not improve the cold flow

properties of M. peregrina methyl ester as the diesel fuel itself

had a high cloud point, pour point and cold filter plugging point.

3.6. Thermal stability of the biodiesel and the blends

The ignition quality of a fuel, basically, is affected by the ther-

mal characteristics of the fuel [42]. TGA can be used to predict

the behavior of the fuel as the initial temperature of volatilization

can be obtained from the onset temperature (T onset ) [43]. The inter-

cept of extrapolated horizontal line at 1% volatilization with the

tangent of the downward part of the weight curve was taken as

the T onset [44]. Fig. 3 depicts the TGA/DGT of the M. peregrina

methyl ester whereas Table 6 shows the onset temperature and

offset temperature of the volatilization for the crude oil, biodiesel

and the blends.

From Fig. 3 it can be seen that M. peregrina methyl ester was

stable until the temperature 125 C as another evidence for the

complete removal of moisture and methanol during the purifica-

tion process. The onset temperature of volatilization was observed

at 193.36 C which is very close to the boiling point of methyl

oleate (190 C) [45], the main component of M. peregrina

methyl

ester as mentioned above. From the DTG curve, M. peregrina

methyl ester showed a single step of volatilization in a very narrow

range of temperature (193.36–231.14 C) with a maximum rate of

mass loss (24.84.53%/min) at 220.84 C. During this stage, 97.83%

of mass loss was observed due to volatilization of M. peregrina

methyl ester. This amount of mass loss is comparable to the ester

content (97.79%) that was determined by the GC analysis.

According to Table 6, crude M. peregrina seed oil had a high

onset volatilization temperature of 374.69 C. The onset of volatil-

ization of the crude M. peregrina seed oil was, drastically, reduced

to 193.36 C by the transesterification reaction. However, the vola-

tility of M. peregrina methyl ester still considered low compared to

the diesel fuel. Referring again to Table 6 it can be seen that the

volatility of the biodiesel was improved, significantly, as the frac-

tion of diesel fuel increased in the blends. Among the blends, B5,

B10, and B20 showed volatilization behavior similar to the diesel

fuel.

From TGA analysis we can conclude that the pure methyl ester

of M. peregrina has low volatility compared to the diesel fuel, how-

ever, M. peregrina methyl ester is a promising, alternative, fuel in

term of engine performance as it showed spontaneous single step

of decomposition. The multiple step of burning usually, indicated

by more than one step of volatilization in the DTG curve, may cause

operational troubles in the engine [46].

0

1

2

3

4

5

6

k e n i m a t i c v i s c o s i t y

( m m

2 / s )

a

800

820

840

860

880

D e n s i t y ( k g / m 3 )

b

36

38

40

42

44

46

48

C a l o r

i f i c v a l u e ( M J / k g )

c

0

20

40 60

80

100

120

140

160

180

F l a

s h p o i n t ( ° C )

d

0

2

4

6

8

10

12

14

16

T e m p e r a t u r e ( ° C )

e

Cloud point

Pour point

CFPP

Fig. 2. Effect of blending on (a) kinematic viscosity, (b) density, (c) calorific value, (d) flash point and (e) cold flow properties.



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4. Conclusions

In this study we have described a new species i.e. M. peregrina

from Moringacea for biodiesel production. The crude oil was, easily

converted to methyl esters by one step alkaline-catalyzed transe-

sterification reaction. The physicochemical characteristics of the

produced biodiesel conformed to the major standards required

by ASTM D6751.The prominent features of M. peregrina methyl

ester were the high oxidative stability and cetane number. More-

over, the fuel properties of the M. peregrina methyl ester were

enhanced significantly by blending with diesel fuel. The fuel prop-erties and the thermal behavior of blends contained up to 20% bio-

diesel, were similar to those of diesel fuel. Therefore, with the

added advantage of the edibility of all other parts, M. peregrina is

a promising source for sustainable production of biodiesel. As such,

more research is needed to optimize the oil extraction, as well as,

biodiesel conversion and to develop a commercial production

process.

Acknowledgments

This work is a part of scientific collaboration between Univer-

sity of Malaya and Sudan University of Science and Technology.

The work was carried out under the Center of Separation Science

and Technology (CSST) and was supported by the University of Malaya’s HIR Grant No. VC/HIR/001/2. Nile Valley University and

Sudan Higher Education Ministry are gratefully acknowledged for

allocating scholarship for the first author.

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Fig. 3. TGA and DTG curves of M. peregrina methyl ester.

Table 6

Volatilization temperatures from TGA analysis.

Fuel On set temperature T on (C) Offset temperature T off (C)

CMPSOa 374.69 418.12

B100 193.36 231.14

B80 193.31 235.48

B60 185.04 231.56

B40 170.56 228.18

B20 141.94 214.61

B10 135.06 216.97

B5 116.62 200.13

B0 108.86 198.37

a Crude M. peregrina seed oil.


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