An economically viable synthesis of biodiesel from a crude Millettia pinnata oil of Jharkhand, India as feedstock and crab shell derived catalyst

Bioresource Technology 214 (2016) 210–217

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Bioresource Technology journal homepage: www.elsevier.com/locate/biortech

An economically viable synthesis of biodiesel from a crude Millettia pinnata oil of Jharkhand, India as feedstock and crab shell derived catalyst Devarapaga Madhu a, Supriya B. Chavan b, Veena Singh a, Bhaskar Singh c, Yogesh C. Sharma a,⇑ a b c

Department of Chemistry, Indian Institute of Technology (BHU) Varanasi, Varanasi 221005, India Department of Chemistry, Bhagwant University, Ajmer 305 004, Rajasthan, India Department of Environmental Sciences, Central University of Jharkhand, Ranchi 83400, India

h i g h l i g h t s

g r a p h i c a l a b s t r a c t


Crude commonly found in Jharkhand

used as a feedstock.
A heterogeneous catalyst derived

from crab shell used for transesterification.
High yield of biodiesel obtained.
Catalyst usable up to 5 times without loss of activity.
Entire process is economically viable.

a r t i c l e

i n f o

Article history: Received 5 February 2016 Received in revised form 11 April 2016 Accepted 12 April 2016

Keywords: Solid waste catalyst (SOD) Karanja oil Biodiesel FTIR Reusability

a b s t r a c t Biodiesel has emerged as a prominent source to replace petroleum diesel. The cost incurred in the production of biodiesel is higher than that for refining of crude oil to obtain mineral diesel. The heterogeneous catalyst was prepared from crab shells by calcining the crushed mass at 800 °C. The solid waste catalyst was characterized with XRD, XPS, BET, SEM–EDS, and FT-IR. Millettia pinnata (karanja) oil extracted from its seeds was used as a feedstock for the synthesis of biodiesel. Biodiesel was synthesized through esterification followed by transesterification in a two-step process. Characterization of biodiesel was done using proton NMR spectroscopy. Reaction parameters such as reaction time, reaction temperature, concentration of catalyst and stirrer speed were optimized. Reusability of catalyst was checked and found that there was no loss of catalytic activity up to five times. Ó 2016 Published by Elsevier Ltd.

1. Introduction Since the last century the demand of energy has escalated because of the change in the lifestyle and exponential growth of population. The fuel consumption has increased several folds and in expected to rise future (Bilgen, 2014). Most of the present energy needs are supplied through natural gas, petrol, diesel and coal. As the availability of these natural resources are finite, the current usage rates will cause fossil fuel depletion (Höök and

⇑ Corresponding author. E-mail address: [email protected] (Y.C. Sharma). http://dx.doi.org/10.1016/j.biortech.2016.04.055 0960-8524/Ó 2016 Published by Elsevier Ltd.

Tang, 2013). The depletion leads to further increase in price of the fossil fuels which are left over. The limited availability of fossil fuels and the escalating demand for energy has led to search for alternative sources of energy which would be environmentally safer and economically viable and socially equitable. Major contributors to this increase in energy demand have been basic industry and transportation sectors. Transportation sector is a major consumer of petroleum fuels like petrol, diesel, and gasoline, liquefied petroleum gas (LPG) and compressed natural gas (CNG). The demand for fuel in transportation sector is poised to escalate in coming years. This could be attributed to increase in number

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of vehicles and rising demand of energy due to emerging economies worldwide. Biodiesel controls emissions of toxic contaminants and carcinogens (Dorado et al., 2003). Synthesis of biodiesel with high purity is not only a major challenge for manufacturers but also a big challenge for scientists and researchers. Synthesis of biodiesel via esterification and transesterification proceeds through different pathways. To achieve a high yield and high conversion of biodiesel, one has to understand the mechanism of the process and optimize the variables affecting the reaction. Biodiesel can also be synthesized without catalyst via subcritical (Zexue et al., 2013) and supercritical methods (Demirbas, 2005). Production of biodiesel is possible at above or the critical values of pressure and temperature of alcohol. The reaction does not lead to the formation of soap due to absence of catalyst. Another advantage of supercritical alcoholysis is that it takes lesser time to produce biodiesel as compared to conventional catalytic methods viz. solid base transesterification (Kusdiana and Saka, 2001). Nevertheless, the main demerits are requirement of huge amount of alcohol and energy consumption. In recent years, biodiesel production through solid-base heterogeneous catalyst such as Li4SiO4, and LiAlO2 are used in transesterification since they show greater basic strength and high activity. Previous studies have shown that the reusability of these catalysts up to ten times without loss of activity since dissolved methanol can be easily separated from these catalysts. Low viscous nature of Li4SiO4, LiAlO2 catalysts facilitates the increase in mass transfer which will contribute more biodiesel yield. Basic strength of Li4SiO4, and LiAlO2 are low when compared to CaO, however a small decrease in basic strength was observed in case of CaO when it is exposed to air for a long time. Synthesis of CaO from crab shell is simple and low cost method when compared to synthesis of above catalysts (Li4SiO4, LiAlO2). Enzymatic reactions for synthesis of biodiesel are environmentally friendly as the side products of these reactions are less. This minimizes the waste generation. In such reactions, the immobilized lipase is used as catalyst for transesterification reactions and esterification with an alcohol. The main problem with the enzymatic reactions is the high cost of bio-catalyst which escalates the overall production cost of biodiesel. Biodiesel derived from oil or animal fats by transesterification with alcohol (viz. wood spirit and ethyl alcohol) is usually recommended to be used as a substitute for mineral (Altın et al., 2001). It helps to reduces emissions of the prominent greenhouse gas, carbon dioxide. Biodiesel has no aromatics, nearly no sulfur, possesses high cetane number than mineral diesel (Canakci and Van Gerpen, 2001). In the present work, biodiesel has been synthesized from Millettia pinnata (karanja) oil using calcium oxide as a catalyst. Calcium oxide is a stable catalyst for the synthesis of biodiesel (Kouzu et al., 2008).

2. Materials and methods 2.1. Chemicals and raw materials Karanja seeds were collected from local market in Varanasi, India. Methanol and sulphuric acid were purchased from Merck India with purity >99%. Crab shells were collected from the coastal regions of Andhra Pradesh, India. Karanja oil was extracted from its seeds through solvent extraction process as per the method given by Bobade et al. (2013). The catalyst (calcium oxide) was prepared from the waste crab shells. The waste crab shells were collected and crushed into powder form. It was then calcined at 900 °C. Esterification followed by transesterification reactions were carried out for the synthesis of biodiesel.

2.2. Catalyst preparation The collected crab shells were thoroughly washed with hot water to remove the impurities present on them. Crab shells were dried and kept in a hot air oven at 110 °C for 12 h. The dried crab shells were ground into powder using ball mill apparatus. The powder was calcined at in a furnace up to 900 °C. Complete conversion of calcium carbonate (CaCO3) into calcium oxide (CaO) occurred when the calcination temperature reached 900 °C. Calcium oxide derived from the crab shells was used in the transesterification process. Calcium oxide as catalyst is reported to be thermally stable and possesses good catalytic activity towards the transesterification process (Boey et al., 2011).

2.3. Catalyst characterization Calcium oxide (CaO) derived from the crab shells was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), Brunauer–Emmett–Teller (BET) surface area, differential thermal analysis/thermogravimetric analysis (DTA/TGA), and Fourier transform infrared spectroscopy (FT-IR). We also calculated the basic strength of CaO derived from crab shell. Calcium oxide was characterized at different calcination temperatures.

2.4. Oil extraction Researchers have reported extraction of oil from the seeds Pongamia pinnata (Bobade and Khyade, 2012), and Citrullus colocynthis (Chavan et al., 2014). The collected karanja (M. pinnata) seeds were dried at 110 °C for 2 h to remove moisture content. The seeds were then grounded in a ball mill apparatus, further this flour was used in solvent extraction process (Bobade et al., 2013). Solvent extraction process was carried out in a soxhlet apparatus which was fitted with 500 ml round bottom flask and cooling condenser. Karanja oil was extracted using petroleum ether as a solvent. The ratio of solute to solvent was 1:6 (50 g of flour and 300 ml of petroleum ether). This solvent extraction process was carried out at 70 °C for 4 h as shown in Table 1. After completion of extraction, solvent was removed with the rotavapor and the extracted karanja oil was taken out for synthesis of biodiesel.

2.5. Pretreatment of karanja oil Extracted karanja oil was subjected to pretreatment for removal of impurities. Karanja oil was filter with Whatman filter paper to remove suspended solid matter present in karanja oil. Water content in karanja oil was removed with rotavapor after these steps; karanja oil was used for synthesis of biodiesel.

Table 1 Solvent extraction of karanja seeds using different solvents. Solvent (10 mL/g of seed) Hexane

Petroleum ether

Diethyl ether

Weight of seed (g)

Extraction time (h)

Weight of crude oil (g)

Yield of oil (%)

10.01 10.05 10.07 10.03 10.08 10.06 10.03 10.05 10.06

3 4 5 3 4 5 3 4 5

4.12 4.29 4.32 4.31 4.40 4.38 4.18 4.32 4.39

41.15 42.68 42.89 42.97 43.65 43.53 41.67 42.98 43.63

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2.6. Fatty acid composition

Table 3 Fatty acids and their composition (%) of karanja oil.

After pre-treatment, the physical and chemical properties of karanja oil were determined and are shown in Table 2. The content of fatty acid is another important characteristic that reflects the quality of karanja oil (Table 3). The fatty acid composition of crude oil influences the cetane number and cold flow properties of biodiesel (Ramos et al., 2009). The fatty acid composition of the oil was determined using Gas Chromatography Mass Spectra. The peaks obtained were identified using the standards of fatty acids. The karanja oil was found to contain both saturated and unsaturated fatty acids. Oleic acid was found to constitute highest composition (44.7%) followed by linoleic acid (32.8%), palmitic acid (14.2%) and stearic acid (7.0%) as shown in Table 3.

2.7. Esterification and transesterification reactions Acid value of karanja oil was 6.04 mg KOH/g. Due to high acid value of karanja oil; esterification reactions were conducted to reduce the acid value. Esterification reactions were carried out using 3 necked round bottom flask of 500 ml capacity placed in a serological water bath attached with magnetic stirrer at 650 rpm. The variables affecting the reaction were optimized. After completion of esterification reaction, the mixture obtained was transferred into separating funnel. Acid and water content were removed from bottom of separating funnel and the remaining water was removed with rotavapor. Acid value of the product was calculated using Eq. (1).

Acid Valueðmg KOH=gÞ ¼ V KOH  56:1  C KOH =msample

ð2Þ

where AV1 (mg KOH g1) is the acid value of original oil sample, and AV2 (mg KOH g1) is the acid value of catalyzed product. Transesterification reactions were conducted after esterification using calcium oxide as a catalyst which is derived from crab shell.

Table 2 Physical and chemical properties of karanja oil. Property

Unit

Color Odor

– –

Acid value

mg KOH/ g mg KOH/ g % w/w – g/cm3 kcal/kg °C mm2/s

ASTM D 664

ASTM ASTM ASTM ASTM

D D D D

°C in % °C °C – –

ASTM – – ASTM ASTM ASTM

D 93

in %

ASTM D2709

Saponification value Unsaponifiable matter Specific gravity Density Calorific value Pour point Kinematic viscosity at 40 °C Flash point Ash content Boiling point Cloud point Iodine value Copper strip corrosion Water content

ASTM standards

Value Yellowish red Characteristic odd odor 6.04

Fatty acid name

Formula

Composition (%)

1 2 3 4 5 6 7 8

Oleic acid Linoleic acid Palmitic acid Stearic acid Palmitoleic acid Linolenic acid Arachidic acid Myristic acid

C18:1 C18:2 C16:0 C18:0 C16:1 C18:3 C20:0 C14:0

44.7 32.8 14.2 7.0 0.7 0.2 0.2 0.1

3. Results and discussion A low acid value owing to low content of free fatty acid (<1%) could be subjected to direct transesterification without performing esterification (Hayyan et al., 2010). However, the high acid value of karanja oil, 6.04 mg KOH/g warrants for two step reaction, i.e. esterification followed by transesterification. Acid value of the product obtained after esterification got reduced to 0.71 mg KOH/g. The optimized values during esterification are: reaction time, 200 min; oil:methanol molar ratio, 1:8; and reaction temperature, 65 °C. The H2SO4 concentrations in all reaction were kept constant at 1.0 wt% of catalyst with respect to oil. Optimum reaction parameters during transesterification were: reaction time, 120 min; reaction temperature, 65 °C; and oil: methanol molar ratio, 1:8. In all the reactions 2.5 wt% of calcium oxide with respect to oil was taken. The rate of stirring throughout the reaction was 700 rpm.

ð1Þ

Free fatty acid conversion was calculated using following Eq. (2):

Free Fatty Acid Conversionð%Þ ¼ ðAV 1  AV 2 Þ=AV 1  100

Sr.

3.1. Characterizations of the catalyst 3.1.1. TGA/DTA 10.517 mg powdered uncalcined crab shell was taken for DTA/ TGA analysis. The temperature range of calcination began from 27 °C (room temperature) to 1100 °C (Fig. 1). As the temperature was increased, weight loss of the catalyst was observed. A signification weight loss was observed at temperature, 350 °C. The maximum weight loss (8.39%) was observed between 325 °C and 500 °C which can be attributed to decomposition of calcium carbonate into calcium oxide by liberation of carbon dioxide. A slight decomposition was observed up to 900 °C and the final weight loss at this temperature was 9.04%. The negligible amount of weight loss occurred when heating continued till 1100 °C. The first derivative, DTA was observed at around 350 °C. This could be attributed to the decomposition of Ca(OH)2. As CaO began to form at temperature 325 °C, a part of it is spontaneously converted to Ca(OH)2. Sharma et al. (2010) reported decomposition of Ca(OH)2 chicken eggshell at 480 °C through the value obtained from DTA.

198

1298 4809 97 445

D 2500 D 1510 D130

2.4 0.923 0.921 8746 1 43.6 227 0.06 320 2.4 84 No corrosion observed 0.005%

3.1.2. XRD analysis Calcination temperature plays a major role in decomposition of calcium carbonate into calcium oxide. Fig. S1. (see Supplementary Material) represents the X-ray diffraction (XRD) peaks of crab shell catalyst calcined at three temperatures i.e. 450 °C, 650 °C and 850 °C. The peaks for catalyst calcined at 450 °C appeared in spectra at 2h = 23°, 29.4°, 36°, 39.4°, 43.1°, 47.5° and 48.5° which were characteristics of calcium carbonate (JCPDS 85-1108) (Fig. S1(1a)). When calcined at 650 °C, the peaks characteristics of calcium oxide were observed. In addition to peaks of calcium oxide, there were few peaks characteristics of calcium carbonate as well (Fig. S1 (1b)). The complete decomposition of calcium carbonate to calcium oxide occurred at calcination temperature of 850 °C. Calcium

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Fig. 1. TGA/DTA of uncalcined crab shell.

carbonate peaks disappeared completely and the peaks obtained at 2h = 32°, 37.3°, 53.8°, 64.4°, 67.3° (JCPDS 48-1467) were of calcium oxide (Fig. S1(1c)).

3.1.3. FT-IR analysis Fig. S2 (see Supplementary Material) represents the Fourier transform infrared spectroscopy (FT-IR) spectra of crab shell calcined at 850 °C. The sharp infrared band occurred at 500 cm1 is a stretching vibration mode of CaAO. Infrared band at 1710 cm1 indicates the presence of carbonyl group (C@O) that indicates that some amount of calcium carbonate present at the calcination temperature 650 °C. When the calcination temperature was increased from 650 °C to 850 °C, the carbonate peak disappeared and complete decomposition of carbonate into calcium oxide was visualized. Infrared band at 700 cm1 clearly indicates the presence of Calcium oxide (CaAO) stretching vibration mode (Sharma et al., 2010). An infrared band at 2357 cm1 attributes the presence of C@O functional group owing to stretching vibration mode (Sharma et al., 2010). A similar peak at 2357 cm1 was observed in the present study. However, the peak was sharp from the catalyst calcined at 650 °C. A sharp OH stretching band was observed at 3625 cm1 for the catalyst calcined at 850 °C. This could be attributed to stretching vibration of structural water molecules. This also indicates that the conversion of CaO to Ca(OH)2 due to presence of water molecules in form of moisture in ambient air.

3.1.4. XPS analyses of CaO derived from crab shell In order to determine the elemental composition of Ca and O from CaO derived from crab shell, the product was analyzed by X-ray photoelectron spectroscopy (XPS). The XPS spectra of Ca (2p) is shown in Fig. 2a. All the XPS spectra were measured with accuracy of ±0.2 eV. The XPS intense peaks occurring at 345.97 eV and 349.51 eV correspond to Ca 2p3/2, and Ca 2p1/2 respectively (28). These intense peaks confirmed the existence of elemental state of Ca ion in the catalyst. Fig. 2b shows the XPS spectra of O (1s). The single peak centered at 530.31 eV corresponds to O(1s) of calcium oxide derived from crab shell. It indicates complete conversion of CaCO3 to CaO by the absence of XPS spectra of C(1s). The elemental composition of calcium and

oxygen derived from crab shell was confined from the above XPS spectra of Ca (2p) and O(1s). 3.1.5. SEM analysis The catalyst (calcined at 850 °C) was characterized on scanning electron microscopy (SEM) to determine the particle size and surface structure (Fig. S3). The morphology of the catalyst was observed to be irregular i.e., there was no regular arrangement of particles. This irregular structure could be attributed to high calcination temperature. A plot was drawn between the frequency of particles vs size. The plotted values indicated that the size of the particles of catalyst was in the range 0.93–2.6 lm but maximum particles were in the range 1–1.8 lm. Bazargan et al. (2015) have reported the size of CaO obtained from palm kernel shell biochar to lie in the range 1–100 lm. The shape of the powder was also reported to be non-uniform. Vujicic et al. (2010) has reported that the calcination temperature of 800 °C is necessary for the development of the CaO texture and a higher temperature (>900 °C), could lead to sintering of the catalyst. 3.1.6. EDS analysis of CaO catalyst Elemental analysis of CaO derived from crab shell was characterized by energy-dispersive X-ray spectroscopy (EDS) which is well known analytical technique to determine the chemical or elemental characterization of a material. Fig. 3 represents the EDS of CaO derived from crab shell. It shows that the calcium carbonate of the crab shell was completely converted into calcium oxide after calcination since there is no carbon peak appeared in EDS spectrum. The weight percentage of calcium obtained from EDS spectrum was 62.14%, while oxygen was 37.86% which clearly indicates the presence of calcium and oxygen in the sample (Table 4). The atomic percentage of calcium observed from EDS spectrum was 60.41% and that of oxygen was 39.59%. 3.1.7. Brunauer–Emmett–Teller (BET) surface area of CaO catalyst Brunauer–Emmett–Teller (BET) surface areas of CaO derived from crab shell was measured by nitrogen gas adsorption–desorption isotherms at 196 °C. Fig. 4a represents the isotherm linear plot drawn in between relative pressure (P/Po) vs quantity adsorbed (cm3/g STP). The surface area of CaO catalyst was found

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Fig. 2. XPS analysis of elemental Ca (2a) and elemental O (2b) derived from crab shell.

Fig. 3. EDS spectrum of CaO catalyst derived from crab shell.

Table 4 % weight of element dispersion in calcium oxide catalyst derived from crab shell by EDS. Element

Weight%

Atomic%

OK Ca K Total

37.86 62.14 100.00

60.41 39.59

to be 16.4775 m2/g and the pore volume of CaO catalyst was found to be 0.032475 cm3/g (Fig. 4b). The adsorption average pore width of catalyst was found to be 78.8351 Å. According to Dubinin– Radushkevich equation, micropore surface area and monolayer capacity were determined and were found to be 5.577334 m2/g, 1.281204 cm3/g respectively.

3.1.8. Basic strength of CaO catalyst Basic strength of CaO derived from crab shell was determined by well-known Hammett indicator titration. 25 mg of CaO catalyst was added to 2 ml of Hammett indicator which was dissolved in methanol and was held for two hours to make equilibrium solution. Here Hammett indicator includes 2,4-dinitroaniline (pKa = 15), indigo carmine (pKa = 12.2), and phenolphthalein (pKa = 9.8). Basic strength of CaO derived from crab shell was found to be higher than that of the weakest indicator in which color change occurred and lower than that of the stronger indicator in which no color change was observed. Basic strength of CaO catalyst

from the above Hammett indicator titration method was found to be 12.1 < H_15.0. 3.2. Effect of reaction parameters on biodiesel yield 3.2.1. Effect of catalyst concentration on biodiesel yield The amount of catalyst has a significant role in transesterification reaction. The influence of amount of catalyst on biodiesel yield is demonstrated in Fig. 5a. The effect of catalyst concentration ranging from 1 wt% to 3.0 wt% with respect to oil was studied under constant reaction conditions: temperature, 65 °C; oil to methanol molar ratio, 1:8; reaction time, and 120 min, respectively. As the catalyst amount was increased from 1 wt% to 2.5 wt%, an increase in biodiesel yield was observed. A sufficient catalyst amount renders higher chances of its contact with reactants (Wu et al., 2014). Methanol, when mixed with oil forms a well dispersed emulsion droplets which on contact with the catalyst particles lead to a sequence of reactions in synthesis of biodiesel (Zhang et al., 2015). A high biodiesel yield was obtained with 2.5 wt% of catalyst. With further increase in catalyst amount, there was no significant increment in biodiesel yield. Biodiesel production decreased when catalyst amount was increased from 2.5 wt % to 3.0 wt% at molar ratios 1:8 and 1:12. This could be attributed to viscous nature of catalyst and reactants which led to the difficulty in mixing (mass transfer) (Tang et al., 2011). 3.2.2. Effect of molar ratio (oil:methanol) on biodiesel yield Effect of molar ratio of methanol to oil on biodiesel production was studied (Fig. 5a). Excess of methanol will facilitate the high

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215

Fig. 4. BET surface areas of CaO catalyst (4a), pore volume (4b) respectively.

Fig. 5. (a) Effect of molar ratio as well as catalyst concentration on biodiesel yield. (b) Effect of reaction time on biodiesel yield. (c) Effect of reaction temperature on biodiesel yield. (d) Effect of stirrer speed on biodiesel yield.

conversion of biodiesel (Ferrero et al., 2015), since methanol molecules will contact easily with triglycerides and reaction proceeds to formation of biodiesel. A high ‘methanol:oil’ molar ratio is thus required to get high conversion of triglyceride into biodiesel (Freedman et al., 1986). In order to determine the effective oil: methanol molar ratio, all the reactions were conducted at calcium oxide (CaO) weight of 2.5 wt% and fixed reaction time of 120 min and at stirring speed of 700 rpm. Oil:methanol molar ratio was

varied from 1:4 to 1:12 at the fixed reaction temperature, 65 °C. Biodiesel production increased from 59% to 94% when the oil: methanol molar ratio increased from 1:4 to 1:12. Biodiesel production decreased when the oil:methanol molar ratio was increased from 1:8 to 1:12. The decrease in biodiesel production at a high molar ratio (1:12) can be attributed to glycerol produced during the reaction that would dissolve in the methanol and inhibit the interaction of methanol with catalyst (Boey et al., 2009). Another

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factor that causes reduction in biodiesel production could be attributed to viscous nature of the reaction mixture and the accumulation of methanol (Meher et al., 2006).

nol when stirrer speed increases inhibiting the interaction between the reactants and methanol (Roy et al., 2014). 3.3. Separation and purification of biodiesel

3.2.3. Effect of reaction time on biodiesel yield Effect of reaction time on biodiesel production was studied at different time intervals ranging from 30 min to 180 min at 1:8 (oil:methanol) molar ratio and 2.5 wt% of catalyst at 65 °C (Fig. 5b). In order to determine the effective reaction time the stirring rate was kept at 700 rpm. Biodiesel yield increased with reaction time up to 120 min since biodiesel production increase with increase in reaction time (Freedman et al., 1984). Maximum biodiesel yield 92% was observed at the end of 120 min. Further, reaction time was increased from 120 min to 180 min but there is no significance increase in the biodiesel production because longer time can be assumed to produce soap via hydrolysis of ester (Leung and Guo, 2006). 3.2.4. Effect of reaction temperature on biodiesel yield Fig. 5c represents the effect of temperature on biodiesel. The transesterification of karanja oil using 2.5 wt% of CaO catalyst was carried out at different temperature ranging from 35 °C to 85 °C with oil:methanol ratio, 1:8; reaction time, 120 min at 700 rpm. Biodiesel production gradually increased with increase in temperature from 35 °C to 65 °C. A sharp increase in the biodiesel production was observed when the temperature rose from 35 °C to 55 °C. A high biodiesel production (93%) was achieved at a moderate reaction temperature of 65 °C. Transesterification reaction has been reported to be affected with the rise of temperature (Okitsu et al., 2013; Patil et al., 2011). An increase in reaction temperature increases the production of biodiesel (Helwani et al., 2009). When the reaction temperature was increased from 65 °C to 85 °C, biodiesel production decreased due to vaporization of methanol which decreased the methanol amount in contact with reactants in transesterification reaction (Meher et al., 2006). 3.2.5. Effect of stirrer speed on biodiesel yield The mixing intensity was observed at stirring rate ranging from 300 rpm to 800 rpm. Effect of stirrer speed on biodiesel production was investigated using 2.5 wt% of catalyst and oil:methanol (1:8) molar ratio in 120 min at 65 °C (Fig. 5d). Stirrer speed ranging from 300 to 700 rpm was effective in all transesterification reactions (Mjalli and Hussain, 2009). A high biodiesel production was obtained when the stirrer speed was 700 rpm. With further increase in stirrer speed from 700 rpm to 800 rpm, no significant increase in biodiesel production was observed. This reduction in biodiesel production may be attributed to vaporization of metha-

The synthesized biodiesel was separated from its by-products in a separating funnel. A small increase in basicity of biodiesel occurred due to the presence of trace amount of base solid catalyst, CaO. Centrifuge and filtration steps were carried out to remove solid suspended matter (solid base catalyst and soap) in biodiesel. The crude biodiesel was washed with distilled water. Water content that remained in biodiesel was removed with rotavapor. Further, biodiesel properties were evaluated according to US Biodiesel Standards. Biodiesel properties were characterized using ASTM standards. It was observed that density reduced from 0.921 (karanja oil) to 0.81 (biodiesel) and the flash point, pour points were 184 °C, and 2 respectively. Kinematic viscosity at 40 °C was reduced from 43.6 (mm2/s) to 4.02 (mm2/s), since density is directly proportional to viscosity. The calorific value of biodiesel was 3800 kcal/kg and the moisture content was found to be 0.005%. The synthesized biodiesel completely complied with the US biodiesel standard as shown in Table 5. 3.4. Catalyst reusability Catalyst was reused in two ways. In the first method, the used catalyst was washed with methanol and calcined at 850 °C and reused up to five times. In the second method, used catalyst was washed with methanol, and reused without calcination up to five times as shown in Fig. 6. In the first method, the catalyst gave 89% of biodiesel yield which was maximum yield in the first run. A minor decrease in the biodiesel yield (84%) was observed in the fifth run in first method. In the second method, the catalyst

Fig. 6. Effect of reusability of catalyst on biodiesel yield.

Table 5 Physical and chemical properties of biodiesel. Properties Kinematic viscosity at 40 °C Specific gravity at 25 °C Density at 15 °C Calorific value Pour point Flash point Acid value Cetane number Cloud point Total glycerin (wt% max) Total sulfur content Phosphorous content Iodine value Copper strip corrosion Water content

Units 2

mm /s °C g/cm3 kcal/kg °C °C mg/KOH – °C in % (ppm), max (ppm), max (g/I2 100 g) – in %

ASTM standard

Karanja methyl ester biodiesel value

ASTM D 445 – ASTM D 1298 ASTM D 4809 ASTM D 97 ASTM D 93 ASTM D664 ASTM-D 613 ASTM D 2500 ASTM D 6584 ASTM D 5453 ASTM D 4951 ASTM D 1510 ASTM D130 ASTM D2709

4.02 0.81 0.881 3800 2 184 0.32 53 3 0.12 13 9 91 No Corrosion observed 0.005%

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gave biodiesel yield of 83% which was maximum yield in the first run. Hence, it can be concluded that calcination renders to activate the catalytic sites and improves the yield of biodiesel. 3.5. An economical process for biodiesel synthesis Cost of fuel is one of the most important factor for its acceptance in national and international market. The total cost of biodiesel includes the price of raw material (Dias et al., 2009; Haas et al., 2006), synthesis process involved in production of biodiesel, purification of the product, and its transportation to the outlets for selling (Canakci and Van Gerpen, 1999). A high yield (94%) of biodiesel synthesized from karanja oil using calcium oxide as a catalyst is anticipated to be cost effective mainly due to availability of a non-edible karanja oil and calcium oxide derived from waste crab shells. Reusability of the catalyst up to five times with a high yield could also be assumed to decrease the total cost of biodiesel production. 4. Conclusion Biodiesel from karanja oil has been synthesized using crab shells as solid catalyst. The catalyst was characterized by using sophisticated techniques. Karanja and biodiesel both were also characterized and a high yield (94%) of biodiesel was obtained. The catalyst was stable and was reusable up to five times without significant loss of activity. The optimized reaction conditions were oil:methanol molar ratio, 1:8; reaction time, 120 min; catalyst amount, 2.5 wt%; at 65 °C and 700 rpm. The fuel properties of the biodiesel were determined as per the US biodiesel standards and found to adhere to the specifications. Acknowledgements The authors are thankful to Department of Science and Technology, Govt. of India for sanctioning IBSA project. They alo thank IBDC, Baramati, Pune, Maharashtra for different analysis work. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.biortech.2016.04. 055. References Altın, R., Cetinkaya, S., Yücesu, H.S., 2001. The potential of using vegetable oil fuels as fuel for diesel engines. Energy Convers. Manage. 42, 529–538. Bazargan, A., Kostic´, M.D., Stamenkovic´, O.S., Veljkovic´, V.B., McKay, G., 2015. A calcium oxide-based catalyst derived from palm kernel shell gasification residues for biodiesel production. Fuel 150, 519–525. Bilgen, S., 2014. Structure and environmental impact of global energy consumption. Renewable Sustainable Energy Rev. 38, 890–902. Bobade, S., Khyade, V., 2012. Preparation of methyl ester (biodiesel) from karanja (Pongamia pinnata) oil. Res. J. Chem. Sci. 2231, 606X. Bobade, S., Kumbhar, R., Khyade, V., 2013. Preparation of methyl ester (Biodiesel) from Jatropha curcas Linn oil. Res. J. Agric. For. Sci. Indore, India 1, 12–19. Boey, P.-L., Maniam, G.P., Hamid, S.A., 2009. Biodiesel production via transesterification of palm olein using waste mud crab (Scylla serrata) shell as a heterogeneous catalyst. Bioresour. Technol. 100, 6362–6368.

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