Enhanced biodiesel production from Jatropha oil

Renewable Energy 101 (2017) 111e119

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Enhanced biodiesel production from Jatropha oil using calcined waste animal bones as catalyst Jan Nisar a, *, Rameez Razaq a, Muhammad Farooq a, Munawar Iqbal a, b, Rafaqat Ali Khan c, Murtaza Sayed c, Afzal Shah d, Inayat ur Rahman e a

National Centre of Excellence in Physical Chemistry, University of Peshawar, Peshawar, 25120, Pakistan Department of Chemistry, The University of Lahore, Lahore, Pakistan Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad, 22060, Pakistan d Department of Chemistry, Quaid-i-Azam University, Islamabad, 45320, Pakistan e PCSIR Labs Complex Peshawar, Pakistan b c

a r t i c l e i n f o

a b s t r a c t

Article history: Received 6 April 2016 Received in revised form 9 August 2016 Accepted 24 August 2016

This study is focused on the investigation of animal bones modified with potassium hydroxide (KOH) as heterogeneous solid base catalyst for transesterification of non-edible Jatropha oil. The prepared catalyst was characterized by energy dispersive X-ray (EDX) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA). The prepared catalyst had a high catalytic activity for transesterification. In addition, the catalyst had excellent stability, there by having potential use as a heterogeneous catalyst for biodiesel production from Jatropha oil with a high free fatty acid (FFA) yield. The experimental results revealed the optimal parametric conditions viz. methanol/oil molar ratio, 9:1, calcination temperature, 900 C and catalyst concentration, 6.0 wt % of oil corresponding to a maximum fatty acid methyl esters (FAME) yield of 96.1% at temperature of 70 ± 3 C in reaction time of 3 h. Reusability results of the prepared catalyst confirmed that it could be reutilized up to 4 times without losing much activity, thus giving birth to a potentially applicable possibility in biodiesel production. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Animal bone Heterogeneous catalyst Hydroxyapatite Jatropha oil Transesterification

1. Introduction Energy resources are considered to be the back bone and most vital instrument for socio-economic development of any country. Based on current energy scenario, the world is going towards a global energy crisis in the near future. Energy consumption and energy crisis are increasing day by day due to ever-increasing world population and high speed of economic development. As a result, petroleum reserves are being depleted that result into unstable petroleum prices. Moreover, petroleum being a potential source of carbon dioxide in the environment, leads to global warming and climate change. Therefore, it is essential to search for an energy source which should be renewable and eco-friendly in nature [1]. Among different renewable energy sources, biodiesel is a promising candidate that would probably reduce the dependency on and preserving petroleum. Biodiesel is a renewable, clean,

* Corresponding author. E-mail address: [email protected] (J. Nisar). http://dx.doi.org/10.1016/j.renene.2016.08.048 0960-1481/© 2016 Elsevier Ltd. All rights reserved.

biodegradable, nontoxic, carbon neutral, low pollutant, environment-friendly and carries efficient combustion due to higher oxygen content and higher flash point [2]. Chemically, biodiesel consists of long chain fatty acid methyl esters (FAME), produced as a result of transesterification reaction from renewable feedstocks like oils and animal fats. Different feedstock, such as vegetable oils (edible and nonedible oils), animal's fat and waste cooking oils are commonly used for biodiesel production [2,3]. Presently, biodiesel is mainly produced from edible oil by transesterification reaction. More than 95% of biodiesel feedstock comes from edible oil. However, the use of edible oil for fuel purpose may create the problems of food in developing countries [4]. Therefore, it is essential to search a potential feedstock for biodiesel production. In this context, nonedible oil such as Jatropha oil may be a good choice for biodiesel production because it is non-edible and provides commercially viable alternative to edible oil [5]. Jatropha seed contains 35e40% oil content and 50e60% in the kernel. The oil comprises of about 79% unsaturated fatty acids and 21% saturated fatty acids [6]. Seed of Jatropha plant contains some

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J. Nisar et al. / Renewable Energy 101 (2017) 111e119

chemical elements which possess poisonous and purgative properties that make the oil non-edible and also a good source for biodiesel [7]. The oil from the seeds is potentially the most valuable end product, with properties like: low acidity, good oxidation stability as compared to soybean oil, low viscosity as compared to castor oil and better cold properties as compared to palm oil. In addition, viscosity, free fatty acids and density of the oil and the biodiesel are stable within the period of storage. Jatropha oil is plant based oil that is commonly employed as a raw material for biodiesel production [8]. Jatropha curcas is a member of Euphorbiaceous family which is cultivated in Central and South America, South-East Asia, India, and Africa. As drought resistant plant, it can be cultivated almost everywhere and may also be used for soil erosion control [9]. Homogeneous catalysts are commonly used for biodiesel production from vegetable oils [10]. Homogeneous catalysts are very effective because of their fast reaction rate at mild conditions, low price and high activity [11]. However, they bear several process problems such as soap formation, separation during purification and generate a large amount of waste water during washing [11]. Heterogeneous catalysts are being employed to overcome the problems encountered with homogeneous biodiesel technology. In contrast, heterogeneous catalysts have several process advantages such as easy separation, environment-friendly, lack of toxicity, ability to withstand at high temperature and ease of recycling [12]. However, in case of heterogeneous transesterification the rate of reaction is lesser as compared to homogeneous system due to the diffusion limitations in three phases. In order to minimize mass transfer limitation and to maximize the surface area of catalyst, structure promoters or catalyst supports are to be used which can provide pores for active species and more surface area for transesterification reaction. Different types of supports have been used in heterogeneous transesterification. It has been stated that aluminium oxide [13], zinc oxide [14] and palm shell activated carbon [15] showed favourable support properties for alkali catalysts in biodiesel production. Different researchers synthesized and used different kinds of solid wastes based catalysts (such as mollusk shells, eggshells, calcined fish scale, sheep bone, etc.) in order to produce costeffective catalysts and biodiesel [16e19]. Among these solid wastes, animal bone is one of the best solid wastes that are easily and abundantly available all over the world. Although, the waste bone derived catalysts have shown a reasonable performance and constancy in the reaction, however these catalysts are required in high amount, high methanol/oil molar ratio with longer time for the reaction to occur. All these disadvantages make waste bone derived catalysts practically and economically unsuitable. To overcome these difficulties, it would be imperative to impregnate calcined waste animal bones in an aqueous solution of KOH to make waste animal bone derived catalyst more active and to boost the surface chemical properties of waste animal bones. Calcined animal bones have proved to be highly effective as a catalyst support. The properties of calcined bone make it advantageous for use as catalyst support in transesterification reaction. Calcined bone contains hydroxyapatite [Ca10(PO4)6(OH)2], that is highly porous and also has a large surface area which allows catalyst to disperse over it largely and effectively. Calcined bones can also be used in high pressure and temperature reaction conditions. For solid catalyst among the different bases, KOH has shown high catalytic activity in transesterification reaction and could be supported on bentonite and palm shell activated carbon as solid base catalysts [15,20]. It is obvious from the above literature review that there is no report wherein pure biodiesel of ASTM specifications has been prepared from jatropha curcas oil, using potassium hydroxide catalyst supported on calcined waste animal bones. It is therefore an objective

of the instant invention to prepare biodiesel from non-edible oil (Jatropha curcas oil) by using potassium hydroxide catalyst supported on calcined bones to produce methyl esters from Jatropha oil and to develop cheap technology process for efficient biodiesel production for sustainable energy production. Once loaded with KOH on the ox bones, the acquired potassium hydroxide supported calcined animal bones catalyst displayed higher catalytic activity. Experiments under different reaction conditions, such as methanol/ oil molar ratio, catalyst loading, reaction temperature and reaction time were performed in order to optimize biodiesel yield. 2. Materials and methodology 2.1. Materials The waste animal bones were obtained from butcher shop. Jatropha oil was purchased from a local market. Methanol (99.8%), n-hexane and n-heptane (GC grade), anhydrous Na2SO4 (99%) were procured from Sigma-Aldrich. Pure potassium hydroxide (98.9%) was used as a catalyst and was purchased from Sigma-Aldrich. Sulphuric acid (98% pure) was procured from Acros Organics. Methyl ester reference standards including methyl oleate, methyl palmitate, methyl linoleate, and methyl stearate of 99% purity were supplied by Supelco. Derivatization agent, N-Methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA) (98.5% GC grade) was purchased from the same company. 2.2. Catalyst preparation Waste animal bones were washed with boiled water for almost 4 h to remove the dust, meat and cartilages and then dried in an oven at 110 C for about 5 h. After cooling them at room temperature the bones were crushed in the form of powder using a grinder. Later the powder bones were calcined at variable temperature range (500e1100 C) in a furnace [18]. After calcination the bone powder was soaked with potassium hydroxide solutions of different concentration, in order to boost its surface chemical properties. This process involves forming a slurry mixture of animal bones with KOH aqueous solution. Animal bones soaked in a solution of potassium hydroxide were then gradually heated in a shaker at 200 rpm until water contents evaporated completely. As a result of heating, a hard cake was formed that was crushed and dried at 120 C for 12 h. 2.3. Characterization of catalyst The physico-chemical characteristics of the produced catalysts were determined by various techniques i.e. TG/DTG (Perkin Elmer Pyris 1), N2 adsorption desorption (Micromeritics, ASAP 2020), Xray diffraction (Bruker D8 X-ray diffractometer equipped with a Cu anode), scanning electron micrographs (JSM-5910, JEOL), energy dispersive X-rays (JSM-7610F) and fourier transform infrared spectroscopy (Shimadzu, IR Prestigue-21). 2.4. Transesterification of Jatropha curcas oil Jatropha oil has a FFA content over 2.5 wt %, a pre-treatment step is necessary before the transesterification process. Prior to the start of transesterification reaction, the oil was filtered and heated at 105 C for 1 h to remove the impurities and water contents. For esterification reaction a mixture of methanol and oil in 12:1 M ratio was put into a three necked round bottom flask having a thermometer and magnetic stirrer attached with a water-cooled condenser and stirred at low stirring rate for 90 min at 50 C followed by addition of 0.8% (v/v) sulphuric acid. The reaction mixture


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was then transferred into a separating funnel and shaken well to remove the excess alcohol, sulphuric acid and impurities. For transesterification reaction, the same experimental set up was used as employed for acid esterification. A mixture of methanol and catalyst in designated amount was agitated and heated at 60 C with constant stirring (600 rpm) for 40 min so that activation of catalyst prior to the transesterification reaction took place. The transesterification reaction was carried out using excess alcohol, different molar ratios of methanol to oil for 3 h at 70± oC with constant stirring (600 rpm). After completion of reaction, the mixture was cooled down to room temperature and then filtered. In order to separate the ester phase from glycerol phase, the filtrate was centrifuged at about 3000 rpm for 15 min. Biodiesel was obtained as the top layer while glycerol at the bottom. The biodiesel phase was then purified by distillation in order to recover unreacted methanol in a batch vacuum distillation flask. The traces of alcohol were removed by washing with hot distilled water followed by drying with anhydrous Na2SO4 [18,19]. 2.5. Yield, purity and fuel properties of synthesized biodiesel The yield of biodiesel production obtained through transesterification of Jatropha oil was calculated based on the fatty acid methyl esters (FAME), using the relation shown in Eq. (1).

Yieldð%Þ¼

Weight of biodiesel producedTotal wt: % of FAME Weight of oil

100 (1) Gas Chromatogram (GC-2010 Plus, Shimadzu) fitted with a flame ionization detector (FID) and automated split injector (AOC20i), employed with a capillary column, TRB-1 (30 m 0.25 mm 0.1 mm) was used to check the fatty acid profile of biodiesel. Nitrogen with a flow rate of 21 mL/min was employed as a carrier gas. At first the oven temperature was fixed at 84 C for 5 min, and then it was increased to 280 C at 5 C min1 and then held it for 5 min. The temperatures of detector and injector were held at 250 C. FAME mix standards were employed as an external standard to analyse the methyl ester. The fuel properties of the synthesized biodiesel were tested and compared with ASTM standard methods. 3. Results and discussion

Fig. 1. The TGA profile of animal bones.

stability of the calcined animal bones at or above 900 C. On the other hand, animal bones calcined beyond 1000 C enhanced the sintering effect that ultimately reduced the surface area and resultantly the activity of the catalyst by decreasing the surface area [21,22]. 3.1.2 Scanning electron micrograph The scanning electron micrographs of the uncalcined, calcined and potassium hydroxide supported bones samples are presented in Fig. 2. The morphology of the uncalcined bone looks like mass of aggregates that have less surface area as compared to the bone, calcined at 900 C, which shows some alteration in its morphology. In calcined bone particle size reduction was maximum, exhibiting higher surface area, an important characteristic of a heterogeneous catalyst. The SEM photograph of potassium hydroxide supported bones shows good scattering of potassium hydroxide on the surface of bones. The results indicate that after loading of potassium hydroxide on calcined bone, its particle size reduces and exhibits higher surface area. Moreover, the potassium species were also found highly scattered upon the surface of the calcined bones uniformly.

3.1. Characterization of catalyst 3.1.1. Thermogravimetric analysis To study the influence of calcination temperature on weight loss, the animal bones powder were subjected to thermal analysis (250e1050 C) at heating rate of 10 C/min in N2 atmosphere. The thermogram in Fig. 1 shows a preliminary loss in weight at temperature range of 50e170 C. This indicates the loss of water in the form of evaporation of adsorbed water. The next step indicates the loss in weight in the temperature range of 200e510 C, which is due to the decomposition of macromolecules and removal of organic portion. An additional very small and steady weight loss is also observed in the temperature range 600 Ce900 C. This may be attributed to the formation of gaseous fraction as a result of transformation of bone to hydroxyapatite (HAP). Around 900 C more loss in weight takes place that could be assigned to the transformation of HAP (hydroxyapatite) into b-Ca3 (PO4)2 [17]. Fig. 1 also shows that the bones calcined at 900 C or above, did not indicate any further loss in weight. It confirms the high thermal

3.1.3. X-ray diffraction analysis The XRD-patterns of uncalcined and calcined animal bones are illustrated in Fig. 3. Indexing of the diffraction peaks was completed using a standard JCPDS (Joint Committee on Powder Diffraction Standards) file. The diffractogram of uncalcined bones confirms the existence of two different phases of CaCO3, known as aragonite and calcite. Calcination at 900 C for 5 h has promoted the conversion of the aragonite (CaCO3) phase to calcium oxide CaO [16,23]. The occurrence of calcite (CaCO3) on the surface of a calcined bone along with Ca(OH)2 is caused by carbonation and hydroxylation reactions that takes place due to direct exposure to atmospheric air [24]. XRDdiffractogram from Fig. 3, also confirms the existence of calcium phosphate oxide that was formed through the calcination process of hydroxyapatite. The peaks of calcined bones were compared with the Joint Committee on Powder Diffraction Standards (JCPDS). The peaks at 21.438 , 25.80 , 39.84 , 45.25 , 49.73 , 51.43 , 56.57, 60.12 , 62.94 and 65.12 are attributed to the presence of

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attributed to the Ca(OH)2 phase. The peak at 53.23 is the characteristics of CaO phase in the catalysts [19]. Similarly, XRD-diffractograms of the KOH/calcined bones catalysts are assembled in Fig. 4. The observed diffraction peaks of calcined bones based catalysts show that a weak KOH- support interaction occurred at low KOH contents 10 wt%. This is due to high Ca:P molar ratios. On the other hand, increased KOH content beyond >10 wt% also promoted the formation of a hydroxyapatite PHA phase, which was a supplementary growth as Ca:P decreased at higher KOH. Animal bones when loaded with KOH, clearly shows a new phase of KCaPO4 at 30.37, however no other peaks of KOH was detected in the synthesized catalyst and that might be due to the interaction of KOH with calcined animal bones and the formation of KCaPO4 [26]. Fig. 4 also shows the effect of calcination temperature on the crystallinity of catalyst. When the calcination temperature was increased from 500 to 900 C the crystallinity of the catalyst increased and hence the peak of KCaPO4 was clearly seen in the diffractograms when the calcination temperature was increased from 500 to 900 C. The diffractograms of Fig. 4 also propose the formation of CaO phase at 34.02 that is formed due to ion exchange of calcium ions of bones with potassium ions of KOH at high temperature [27].

Fig. 2. (A) SEM image of uncalcined animal bones (B) SEM image of calcined bones and (C) SEM image of KOH/calcined animal bones.

3.1.4. Energy dispersive X-ray analysis The elemental analysis of pure calcined bones and KOH/calcined bones are illustrated in Fig. 5 and Table 1(a) and (b). The inorganic composition (C/O/Mg/P/Ca) of the different catalysts were determined by OXFORD INCA EDS. EDX analyses revealed that the inorganic phases of bones were mainly composed of calcium and phosphorus with some minor components such as C, Na, and Mg. The results in Table 2 also indicate that the calcium, oxygen and phosphorous contents increase as the temperature is increased and reach a maximum at 900 C, confirming the formation of hydroxyapatite [19]. The EDX analysis of animal bones modified with potassium hydroxide show that K active sites increase from 0.0% to 11.29% as KOH loading to animal bones structure increases. 3.2. Catalyst reusability Reusability of catalyst was examined by carrying out transesterification reaction several times. The used catalyst in 1st time

Fig. 3. (a) XRD pattern of un-calcined animal bones and (b) XRD pattern of calcined animal bones at 900 C for 5 h.

hydroxyapatite [12,25]. The peaks at 28.76 , 30.45 and 31.74 are attributed to b-Ca3(PO4)2 phase, thus confirm the transformation of hydroxyapatite into b-Ca3(PO4)2 that could act as a base catalyst for transesterification reaction [18]. The peaks at 18.60 and 34.02 are

Fig. 4. XRD patterns of all catalyst samples at different KOH loading percent.


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3.3. Biodiesel characterization Physiochemical properties of produced biodiesel from Jatropha oil using KOH/AB as a catalyst were considered and compared with ASTM standard methods. The outcomes of this characterization are listed in Table 3, which meet with standards of ASTM. The relative composition and identity of different fatty acid methyl esters were analyzed by Gas Chromatography (GC-2010 Plus) and FTIR. 3.3.1. Gas chromatography analysis To detect the different fatty acids methyl esters existing in the biodiesel, GC-FID analysis was used by developing a method. The composition of methyl ester in the synthesized biodiesel is presented in the gas chromatogram (Fig. 6). Different peaks appeared in the chromatogram were identified by comparing them with the standards and reported data that agree well with the methyl esters found in the synthesized biodiesel. The chromatogram also confirms the successful conversion of Jatropha oil into biodiesel.

Fig. 5. (a) EDX spectra of calcined bones and (b) EDX spectra of KOH/calcined bones.

Table 1 (a) EDX analysis of calcined bones and (b) EDX analysis of KOH/calcined bones. a Elements

b Weight%

Atomic

(%)

(%)

e

12.18 45.26 0.44 15.21 26.95 e

10.58 59.28 0.87 15.57 13.7 e

Total

100

CK OK Mg K PK Ca K

Elements

Weight

Atomic

(%)

(%)

CK OK Mg K PK KK Ca K

8.93 45.26 0.51 11.14 11.21 22.95

14.73 59.28 0.44 7.54 6.01 12

Total

100

Table 2 EDX analysis of calcined bones at different temperatures ( C). Elements

700 C Weight

800 C

900 C

Atomic

Weight

Atomic

Weight

Atomic

25.31 52.63 0.63 8.82 12.62

17.51 39.30 0.91 13.60 28.69

28.49 48.01 0.73 8.85 14.18

14.48 39.00 0.64 14.26 31.62

24.50 49.56 0.54 9.36 16.04

3.3.2. Fourier-transform infrared spectroscopy analysis FT-IR spectra of the Jatropha oil and the biodiesel produced from this oil are illustrated in Fig. 7. The Jatropha oil indicates a peak at 3410 cm1 conforming the stretching and bending vibration of O-H bonds due to the presence of water molecules. The antisymmetric and symmetric stretching vibrations of C-H in CH2 and CH3 groups can be confirmed by the presence of peaks at 2924 cm1 and 2853 cm1 respectively. The strong peak present at 1743 cm1 is attributed to the presence of C¼O stretching vibration of carbonyl groups that is present in the triglycerides. The peaks at 14001200 cm1 region confirmed the bending vibrations of CH2 and CH3 aliphatic groups. Similarly bending of HCH takes place at 1373 cm1 and CH2 and scissoring at 1466 cm1 respectively. The peaks Table 3 Physical and chemical properties of biodiesel and its comparison with diesel fuel characteristics. Properties

Method

Biodiesel

Diesel

Kinematics viscosity (mm2/s) Density (kg/m3) Acid number (mg KOH/g oil) Moisture content (%) Iodine value (g iodine/100 g) Calorific value (MJ/kg) Flash point ( C)

ASTM D445 ASTM D4052 ASTM D664 ASTM D2709 PORIM ASTM D240 ASTM D93

2.45 869 0.629 0.003 98 39.72 73

2.5 853 e 0.02 93 42 68

(%) CK OK Mg K PK Ca K

15.67 43.40 0.79 14.07 26.07

Total

100

100

100

transesterification reaction was taken out from the reaction vessel and fully dried for reutilization. It was found that the activity of catalyst was still 86% of the 1st time used catalyst, when it was used for fourth time. This is due to the high basicity of KOH/AB (potassium hydroxide/animal bone) catalyst that stopped the further decomposition of b-Ca3(PO4)2 in the reaction mixture. The decomposition of catalyst was attributed to the hydration and leaching of active sites into the reaction mixture. Leaching of active sites are due to the breakage of bond with the creation of CH3O and Kþ ions which is very much negligible in this loss.

Fig. 6. Gas chromatogram of the synthesized biodiesel.

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Fig. 7. FT-IR spectrum of (a) Jatropha oil (b) synthesized biodiesel.

present in the region of 1120e1090 cm1 presented the stretching vibration of C-O ester. The peak obtained at 721 cm1 confirmed the rocking vibration of (CH2)n overlapping [28,29]. Moreover, the peak at1742 cm1 confirmed the stretching vibration of C¼O present in the esters and peaks present in the range of 1300e1000 cm1 conforming to that of the C-O stretching vibrations [30,31]. The stretching vibrations of CH3, CH2, and CH groups can be seen at 2980e2950, 2950e2850 and 3050e3000 cm1, while the bending vibrations of CH3, CH2, and CH groups appeared at 1475e1350, 1350e1150 and 722 cm1 respectively [31,32]. The FT-IR spectra of the Jatropha oil and biodiesel produced from it are comparable to each other because of the presence of triglycerides and esters. However, very small differences were observed where the peaks appeared at 1743, 1373, 1155, 1038 and 876 cm1 in the Jatropha oil were shifted to 1742, 1365, 1172, 1018 and 884 cm1 in the biodiesel respectively. So, the disappearance of the peaks from the spectrum of the Jatropha oil at 1443, 1096 and 965 cm1 and formation of new peaks at 1430 cm1 and 1194 cm1 in the produced biodiesel

sample evidently confirm the conversion of Jatropha oil into biodiesel. Moreover, the absence of a broad peak in the region of 3100e3500 cm1 proposes that the biodiesel synthesized from Jatropha oil contains low water contents. 3.4. Optimization of transesterification over KOH/CAB catalysts 3.4.1. Effect of calcination temperature To observe the effect of the calcination temperature on the catalyst activity, potassium hydroxide impregnated animal bones were calcined at different temperature ranging from 200 to 1000 C. Calcination beyond 600 C did not show any significant change in the activity of catalyst. However, calcination at 900 C increased the crystallinity and optimal active sites of the catalyst that increased the yield of biodiesel up to 96% at 70 ± 3 C within 3 h (Fig. 8). When the calcination temperature was further increased to 1000 C, it resulted in the suppression of catalytic activity due to the high sintering rate of the catalyst and high


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the formation of new phases that were less active [19,34,35]. Hence, the best catalytic performance of the catalyst was obtained at a calcination temperature of 900 C. Sintering rate of catalyst not only reduced the BET surface but also reduced basicity of the catalyst. Thus, the experimental results showed that calcination at 900 C is considered to be the most perfect, appropriate and optimum temperature for the calcination of this particular catalyst.

Fig. 8. Effect of calcination temperature on biodiesel yield.

energy consumption, which was confirmed by decrease in biodiesel production by successive experiments [18,33]. This showed that at higher temperatures, excessive structure collapse and formation of new inactive phases seriously affected the activity of the catalyst. Earlier studies have also found that calcination at 900 C resulted in

3.4.2. Effect of KOH loading To determine the effect of catalyst loading on FAME conversion a series of KOH/CAB catalysts were synthesized by changing the concentration of KOH from 1 to 14 wt %. When the calcined bones were loaded and activated with KOH at higher temperature, they showed higher catalytic activity than the virgin calcined bones (Fig. 9a). By increasing the amount of KOH loading, biodiesel production increased. When the loaded KOH was less than 10 wt %, it did not provide enough catalytic activity because of formation of least basic active site for FAME conversion. However, when the amount of KOH was increased from 10 wt % onward, the catalyst still provided weak catalytic activity due to agglomeration of extreme active sites. These excessive active sites also caused poor scattering of K on the surface of calcined bones and made some active sites unreachable to the substrate [36,37]. Thus, the KOH loading of 10 wt % could be designated as the best value for solid catalyst.

Fig. 9. (a): Effects of KOH loading on the yield of biodiesel (The reaction parameters: catalyst calcination temperature 900 C, 9:1 M ratio of methanol to oil, 70 ± 3 C for 3 h), (b): Effects of catalyst dosage on the yield of biodiesel (The reaction parameters: catalyst calcination temperature 900 C, 9:1 M ratio of methanol to oil, 70 ± 3 C for 3 h), (c) Effects of methanol to oil molar ratio on the yield of biodiesel (The reaction parameters: catalyst calcination temperature 900 C, 6.0 wt % catalyst dosage, 70 ± 3 C for 3 h) and (d): Effects of reaction time on the yield of biodiesel (The reaction parameters: catalyst calcination temperature 900 C, 9:1 M ratio of methanol to oil, 6.0 wt % catalyst dosage, 70 ± 3 s C).

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3.4.3. Effect of catalyst loading To investigate the effect of catalyst loading on FAME conversion, different wt. % of catalyst were loaded (Fig. 9b). Initially when the small amount of catalyst was used, no remarkable conversion occurred. However, when the amount of catalyst was increased from 2 to 6 wt % then the biodiesel yield was increased from 65 to 96.1 and the maximum of 96.1% was achieved by loading 6 wt % of catalyst. But, when the amount of catalyst was increased from 6 wt % onward, the yield dropped to a significant level and led to the formation of viscous slurries to enable adequate stirring [38]. Thus it is indicative of the fact that the optimum catalyst loading is 6 wt % in this study. 3.4.4. Effect of methanol to oil molar ratio In order to drive the reaction to forward side, it is necessary to use excessive methanol because the transesterification reaction is a reversible reaction. When the methanol/oil molar ratio was increased from 3:1 to 13:1, the biodiesel yield increased gradually and significantly. However, the optimum molar ratio of methanol to oil was found to be 9:1 that was due to the formation of methoxy species formed on the surface of catalyst and caused a shift in the equilibrium in the forward direction. While further increasing the molar ratio from 9:1 onward, a decrease in the biodiesel yield was observed as shown in Fig. 9c, and this reduction was attributed to the deactivation of catalyst and difficulty in the separation of biodiesel from glycerol was faced due to high amount of methanol. Hence excessive use of methanol decreased the conversion by shifting the equilibrium in the reverse direction. 3.4.5. Effect of reaction temperature The effect of reaction temperature on biodiesel yield over KOH/ CAB catalyst was examined at different temperatures. Increasing the reaction temperature from 60 to 70 C, an increase in the conversion of oil into biodiesel was noted and maximum conversion of 96.1% was achieved at 70 ± 3 C. Increasing the reaction temperature above 70 C, a reduction in the yield of FAME was observed. This is due to the fact that, when methanol is heated above its boiling point it bubbles out and as a result of this bubbling mass transfer on the interface of the phases inhibits. Hence, the optimum reaction temperature for the transesterification of Jatropha oil in the presence of KOH/CAB was found out to be 70 ± 3 C in the present study. 3.4.6. Effect of reaction time Among others parameters, reaction time is one of the important parameter that has a profound effect on the FAME yield in this transesterification reaction. The catalytic performance of KOH/CAB was examined by varying the reaction time from 0.5 h to 4 h. Fig. 9d, shows that FAME content increased on increasing the reaction time from 0.5 h to 4 h. However, the maximum yield of 96.10% was attained after 3 h and on further increasing the reaction time, the yield of biodiesel started to decline. The lower yield at lesser reaction time is due to the absence of calcium methoxide, which is the main driving force for the transesterification reaction. The optimum reaction time was found out to be 3 h over the catalyst in the present study. Therefore, transesterification using animal bones modified with KOH as heterogeneous solid base catalyst is viable method for the conversion of Jatropha oil into biodiesel, which is a green method to avoid environmental issue related to conventional fuels [39,40]. 4. Conclusion The present study reveals the effective application of potassium hydroxide catalyst supported on calcined animal bones as a

heterogeneous catalyst for biodiesel production from Jatropha oil. Potassium hydroxide impregnated on calcined animal bone effectively catalyzed the transesterification of refined Jatropha oil to produce biodiesel. Furthermore, the prepared catalyst, showed promising reusability, high specific surface area and higher biodiesel yield that could be achieved at moderate methanol to oil molar ratio and lower catalyst amount. Among the different transesterification parameters, catalyst loading and reaction temperature were found to be the most important parameters on production yield. The optimum condition of transesterification using potassium hydroxide catalyst supported on calcined animal bones was 70 ± 3 C reaction temperature, 6.0 wt % of oil catalyst loading and 9:1 methanol to oil molar ratio. Under these optimum conditions 96.01% production yield was obtained. The produced biodiesel under these reaction parameters was characterized and its physiochemical properties were compared with the ASTM standard. As the waste bone catalyst shows high catalytic activity and is simple, economical, ecologically friendly, therefore, it could be utilized as potential catalyst for biodiesel production on industrial scale. Acknowledgement The financial/facility support provided by Higher Education of Pakistan through project No. 20-1491 is gratefully acknowledged. References [1] F. Umbach, Global energy security and the implication for EU, Energy Policy 38 (2010) 1229e12240. [2] P.D. Patil, S. Deng, Optimization of biodiesel production from edible and nonedible vegetable oils, Fuel 88 (2009) 1302e1306. [3] M.G. Kulkarni, A.K. Dalai, Waste cooking oil an economical source for biodiesel: a review, Ind. Eng. Chem. Res. 45 (2006) 2901e2913. [4] K. Prueksakorn, S.H. Gheewala, Full chain energy analysis of biodiesel from Jatropha curcas L. in Thailand, Environ. Sci. Technol. 42 (2008) 3388e3393. [5] E. Akbar, Z. Yaakob, S.K. Kamarudin, M. Ismail, J. Salimon, Characteristic and composition of Jatropha curcas oil seed from Malaysia and its potential as biodiesel feedstock, Eur. J. Sci. Res. 29 (2009) 396e403. [6] I.A. Kartika, M. Yani, D. Ariono, P. Evon, L. Rigal, Biodiesel production from Jatropha seeds: solvent extraction and in situ transesterification in a single step, Fuel 106 (2013) 111e117. [7] H. Wu, J. Zhang, Y. Liu, J. Zheng, Q. Wei, Biodiesel production from Jatropha oil using mesoporous molecular sieves supporting K2SiO3 as catalysts for transesterification, Fuel Process Technol. 119 (2014) 114e120. [8] N.C.O. Tapanes, D.A.G. Aranda, J.W. de Mesquita Carneiro, O.A.C. Antunes, Transesterification of Jatropha curcas oil glycerides: theoretical and experimental studies of biodiesel reaction, Fuel 87 (2008) 2286e2295. [9] S. Tamalampudi, M.R. Talukder, S. Hama, T. Numata, A. Kondo, H. Fukuda, Enzymatic production of biodiesel from Jatropha oil: a comparative study of immobilized-whole cell and commercial lipases as a biocatalyst, Biochem. Eng. J. 39 (2008) 185e189. [10] L.C. Meher, D.V. Sagar, S.N. Naik, Technical aspects of biodiesel production by transesterificationda review, Renew. Sust. Energy Rev. 10 (2006) 248e268. [11] Q. Shu, Q. Zhang, G. Xu, Z. Nawaz, D. Wang, J. Wang, Synthesis of biodiesel from cottonseed oil and methanol using a carbon-based solid acid catalyst, Fuel Process Technol. 907 (2009) 1002e1008. [12] B.E.H.P. Freedman, E.H. Pryde, T.L. Mounts, Variables affecting the yields of fatty esters from transesterified vegetable oils, J. Am. Oil Chem. Soc. 61 (1984) 1638e1643. [13] H. Ma, S. Li, B. Wang, R. Wang, S. Tian, Transesterification of rapeseed oil for synthesizing biodiesel by K/KOH/g-Al2O3 as heterogeneous base catalyst, J. Am. Oil Chem. Soc. 85 (2008) 263e270. [14] W. Xie, X. Huang, Synthesis of biodiesel from soybean oil using heterogeneous KF/ZnO catalyst, Catal. Lett. 107 (2006) 53e59. [15] S. Baroutian, M.K. Aroua, A.A.A. Raman, N.M.N. Sulaiman, Potassium hydroxide catalyst supported on palm shell activated carbon for transesterification of palm oil, Fuel Process Technol. 91 (2010) 1378e1385. [16] N. Viriya-Empikul, P. Krasae, B. Puttasawat, B. Yoosuk, N. Chollacoop, K. Faungnawakij, Waste shells of mollusk and egg as biodiesel production catalysts, Bioresour. Technol. 101 (2010) 3765e3767. [17] R. Chakraborty, S. Bepari, A. Banerjee, Application of calcined waste fish (Labeo rohita) scale as low-cost heterogeneous catalyst for biodiesel synthesis, Bioresour. Technol. 102 (2010) 3610e3618. [18] A. Obadiah, G.A. Swaroopa, S.V. Kumar, K.R. Jeganathan, A. Ramasubbu, Biodiesel production from palm oil using calcined waste animal bone as catalyst,

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