DETERMINATION OF PHYSICO-CHEMICAL PROPERTIES OF CASTOR BIODIESEL A POTENTIAL

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DETERMINATION OF PHYSICO-CHEMICAL PROPERTIES OF CASTOR BIODIESEL  A POTENTIAL Powered By Docstoc
					  International Journal of Advanced Research OF ADVANCED RESEARCH IN
  INTERNATIONAL JOURNAL in Engineering and Technology (IJARET), ISSN
  0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME
             ENGINEERING AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)                                                      IJARET
Volume 4, Issue 3, April 2013, pp. 101-107
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       DETERMINATION OF PHYSICO-CHEMICAL PROPERTIES OF
          CASTOR BIODIESEL: A POTENTIAL ALTERNATE TO
                     CONVENTIONAL DIESEL

                             R.SRUTHI*1, K. RAVI KUMAR2, G. SHIRISHA3
                  1
                      Asst Prof., Department of Petroleum Engineering, AHCET, Chevella,
                                      Ranga Reddy – 515002(A.P.), India.
                 2
                     Asst Prof., Department of Mechanical Engineering, AHCET, Chevella,
                                     Ranga Reddy – 515002(A.P.), India.
                 3
                     Asst Prof., Department of Mechanical Engineering, AHCET, Chevella,
                                      Ranga Reddy – 515002(A.P.), India


  ABSTRACT:

           Depletion of world’s crude oil reserves, increasing crude oil prices, negative effects of
  mineral and synthetic oils on man. Biodiesel is receiving increased attention as an alternative, non-
  toxic, biodegradable and renewable diesel fuel and contributes a minimum amount of net green house
  gases, such as CO2, SO2 and NO emissions to the atmosphere. Exploring new energy resources, such
  as biofuel is of growing importance in recent years. The possibility of obtaining oil from plant
  resources has created a great importance in several countries. Vegetable oil after tansesterification
  being used as bio diesel. Considering the cost and demand of the edible oil is bearable, so it may be
  preferred for the preparation of bio diesel in India.
           In the present study castor oil was exctracted from seeds through soxhlet extraction, fatty acid
  methylesters was synthesized with methanol, KOH as a base catalyst. Product was confirmed with
  1HNMR spectra, physico-chemical properties were determined for oil and its methylesters to compare
  the properties. Physico-chemical properties demonstrate that methylesters are exhibiting improved
  and excellent properties than its oil for bio-diesel purpose. Thermo-oxidative stability and cold flow
  properties were also found, which is showing satisfactory results. From this study it was concluded
  that castor oil can be used as a potential alternate to conventional diesel...

  1.      INTRODUCTION

          Gradual depletion of world fossil reserves and emissions of green house gasses are leading to
  energy insecurity and ecological imbalance in future. Biodiesel derived from renewable resources i.e
  vegetable oils seems to be a resolution as it is ecofriendly in nature.


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Biodiesel can be defined as basically monoalkyl esters of fatty acids produced from animal fats or
vegetable oils by transesterification or other methods with small chain alcohols, using different kinds
of catalysts [1]. Currently, more than 95% biodiesel are produced from edible oil feedstock, due to
this there is a huge imbalance in the human nutrition chain versus fuel [2]. This will make biodiesel
economically unfeasible as compared to petroleum-derived fuels [3,4]. To avoid these situations, non-
edible oil seeds need to be used for commercial production of biodiesel. Many researchers have
initiated work on the use of low cost non-edible oils as alternative feedstock for biodiesel production
[5,6,7]. Among non-edible oil feedstock, seeds of castor proved to be a one of the highly promising
reliable source having high seed oil content. Castor oil is non-edible due to presence of toxic phorbol
esters and curcin [9].
         Therefore, in the present paper efforts has been made to extract the oil from castor seeds,
synthesis of its fatty acid methylesters, determination of physico-chemical properties (fuel properties)
and thermo-oxidative stability analysis of castor for exploration of potential biodiesel sources.

2. MATERIALS AND METHODS

2.1. Materials
        Castor seeds were separated from the fruit mechanically and cleaned manually to remove all
foreign material. The cleaned seeds were dried at 60O C temperature. Pure standards of FAME was
purchased from M/s Sigma Aldrich. All other chemicals and reagents (methanol, ethanol, n- hexane,
potassium hydroxide, and phenolphthalein indicator were analytical reagent grade and purchased from
M/s Merck.

2.2. Extraction procedure of Castor oil
        Castor oil was extracted in soxhlet apparatus using n-hexane as per the standard AOCS
(American Oil Chemical Society) procedure for 8 h. The extract was concentrated in rota vapor, the
residual oil was cooled and weighed. The physico-chemical properties of the oil were determined.

2.3. Transesterification of Castor oil
         Due to low acid value of the oil direct transesterification procedure was followed.
Transesterification reaction was carried out in 250 ml three necked glass vessels (3 mm thick) sealed
tightly and fitted with condenser at the top. The reaction glass vessel was placed on the hot plate
magnetic stirrer. Methyl esters of Castor seed oil were prepared by refluxing the oil at 60OC
employing a 1:6 molar ratio of oil to methanol for one and half hour with 1 wt% KOH as catalyst and
the mixture was stirred using a magnetic stirrer at 400 rpm [10]. After completion of the reaction, the
mixture was cooled to room temperature and poured in a separating funnel, leading to separation of
two phases. The bottom glycerol layer was discarded and the top ester layer was washed gently
several times with warmed water to remove the catalyst, glycerol, and soap. A pH meter was used to
check the complete removal of the catalyst. The washed methyl ester was further purified under
vacuum on a rotary evaporator.

2.4. 1H NMR spectroscopy
         1H NMR spectrum of Castor oil and the fatty acid methyl esters was obtained on 500 MHz
NMR spectrometer. Samples were dissolved in 400 ml deuterated chloroform (CdCl3) and transferred
to the 5-mm NMR tube. The deuterated chloroform chemical shift peak at 7.26 ppm was taken as
internal reference. Typical parameters used were: spectral width: 4800 Hz; time domain data points:
32 K; flip angle: 90O; relaxation delay: 5 s; spectrum size: 32 K points; and line broadening for
exponential window function: 0.3 Hz.




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2.5. Thermogravimetric analysis (TGA)
        The thermogravimetric profile of castor oil and its methyl esters was obtained using
Thermogravimetric Analyzer at the heating rate of 10 OC/min in both nitrogen and air atmosphere.
The sample size was kept almost same 5 to 6 mg throughout the study.
3. RESULTS AND DISCUSSION

3.1. Physiochemical characterization of castor oil
         The physico-chemical characteristics of oil was estimated as per the ASTM standard methods.
Initially, the specific gravity of the oil sample was determined using the standard method mentioned
above. Specific gravity of castor oil was found to be 0.875, which is within acceptable range of
standard ASTM specifications. Similarly, viscosity of oil sample was measured using a standard
protocol. Viscosity of the oil increases with increase in molecular weight and decreases with increase
in unsaturation level and temperature [19]. The kinematic viscosity of the oil at (40 OC) was found to
be 75.40 cst respectively, which is much higher as compared to conventional diesel . These high
viscosity oils cannot be used directly in engine. High viscosity causes injector fouling and other
engine operational problems. Therefore, before application in diesel engine, processing is required to
reduce the viscosity of the oil. The flash point of the oil was found to be 314. The result shows that
the flash point of oil sample is much higher as compared to conventional diesel. Similarly, the fire
point of oil was found at 333 OC which is much higher than diesel. Refractive index is the degree of
the deflection of a beam light that occurs when it passes from one medium to the other. The refractive
index value increases with the degree of unsaturation. Refractive index was found to be 1.46.
Moisture content of oils was determined using Karl fisher titrator. Moisture content is a qualitative
parameter of oil, which influences the storage life of fuel. High moisture content may serve as a
medium for microbial growth. Microbial growth in the oil may leads to damage of tank and emulsion
formation [20]. Besides this, it initiates oxidation of oil which effects longetivity of engines and
reduced shelf life of the oil. The moisture content of the oil was found to be 0.33 which are within
acceptable range of standard values. The flow characteristic of oil was observed under low
temperature. The pour point of 7 OC was observed. The calorific value for the oil was measured in an
oxygen bomb colorimeter. The data obtained from experiment for castor oil showed high calorific
value in the range of 35.46 MJ/Kg. The acid value of the oil determines the process of
transesterfication i.e. either one step or two step process [21]. The acid value of the castor oil was
measured to check the free fatty acid content in the oil sample, and it was found to be 3.23 mg/KOH.
         As per the values reported in the literature FFA content of castor oil varies in the range of 4 to
40 which is far beyond the capacity of conversion to biodiesel via single step alkali catalyzed
transesterification. But in the present study FFA content of oil was found to be very less. So, single
step alkali catalyzed reaction was performed for conversion of oil in to biodiesel. This single step
transesterification yields substantially higher conversion rate and decreased the reagent use and
reaction time as compared to two step transesterification process. The high FFA content increases the
formation of fatty acids salts (soap) and conversion rate decreased which cause problem in separation
of glycerol at washing step.

3.2. Characterization and evaluation of synthesized methyl esters
        The fuel properties of methyl esters of castor oil was determined using the standard protocol.
During the study it was observed that the specific gravity which influences the fuel atomization [21]
was reduced after methanolysis. The obtained values for methyl esters castor oil was within the
acceptable range of ASTM standards . As described above the viscosity which is the major problem in
the oil samples for engine operation was substantially decreased after transesterification. The
decreased value of the viscosity was found to be 12 cst. The values are almost within the acceptable
range of ASTM standards . Similarly, flash and fire point values were also found to be reduced after
transesterification and the obtained Values are in the range of 185 and 190 OC respectively.



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                        Fig.1 1H NMR spectrum of castor oil and methyl ester

         Since, flash point and fire point values are depends on viscosity, therefore, decrease in the
viscosity values after transesterification might be one of the cause for reduction. Acid value is another
measure of qualitative character of biodiesel. As per the ASTM standard, acid value of transesterified
product should not be more than 0.5 mg KOH/g. The acid values of the methyl esters of the castor oil
sample in the present study was found to be 0.46 mg KOH/g, which is below the maximum limits of
the standards . Similarly, the moisture content of the prepared methyl esters samples was determined
using Karl fisher titrator. After transesterification the moisture content of methyl esters was found to
be 0.25% , which is well below the maximum acceptable limits. Cold flow properties such pour point
of methyl ester was found to be improved after transesterification. Pour point of methyl esters was
measured as 2 OC. But these values are still much higher than the conventional diesel. The heating
value is one of the essential properties for evaluation of biodiesel, which provides the suitability of
fuels as alternative to diesel fuels [25]. Calorific value for methyl esters was obtained as 41.36 MJ/Kg.
The result shows that calorific value of methyl esters is higher than the corresponding oils . All these
properties combined together have shown that castor oil could act as the potential candidates for
biodiesel production.

3.3. 1H NMR spectroscopy
         Nuclear magnetic resonance (NMR) spectroscopy was employed to monitor the
transesterification reaction. In case of 1H NMR spectra of methyl esters, signal appears in the region
at 3.7 ppm which indicates the presence methylic esters group [27]. The characteristic peak of
methoxy protons was observed as a singlet at 3.65 ppm and this signal was attributed to methyl esters,
which was absent in the oil. In case of 1H NMR spectra of oil, multiple peaks were observed in the
region 4.11-4.115, 4.266-4.306 ppm and 5.30-5.34 ppm, due to oxymethylic hydrogen that are
characteristic of triglycerides. 1H NMR spectrum of castor methyl esters, the strong singlet peak at
3.659 ppm is indicative of conversion of parent oil to methyl esters. So, from the NMR spectrum of
oil and methyl esters, it could be verified that castor oil conversion into biodiesel was successfully
completed.

3.4. Thermal stability of castor oil and methyl esters
         Thermal stability of castor oil and its methyl esters was determined from onset temperature of
thermal decomposition under nitrogen atmosphere. The curve shows three consecutive stages of
thermal decomposition of the oil samples. The first phase of decomposition start at 310-315 OC and
second phase extended up to 470 OC which leads to rapid weight loss. The final stage of
decomposition, where pyrolyzed product of second phase fully decomposed extended from 470 to 700
O
  C. In the first stage evaporation starts at 240-280 OC, extended up to 540 OC where rapid weight loss


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was occurred. Final decomposition occurred between 540 and 700 OC. TGA analysis of methyl esters
samples was carried out under similar condition.




            Fig.2- TGA profile of castor oil and methyl esters under nitrogen environment

          From the TGA curves of the oil samples and methyl esters it was observed that, the process of
degradation of castor methyl esters initiates and completed within a temperature range inferior to the
respective oil sample. Molecular tension produced by bulky triglycerides molecule in the oil sample
which could be the reason for thermal stability of oil [28]. Besides this, high viscosity might be the
reason for slow degradation process [15]. The poor volatility and high viscosity of the oils are the
major challenges to run modern diesel engines with plant oils. The onset temperature for volatilization
and distillation was calculated from respective TGA curves of castor oil and methyl esters. The result
shows that onset temperature of thermal degradation of methyl esters was lower as compared to oil
sample. In case of oil sample weight loss was negligible below 300 OC. But after that rapid
degradation was observed at 310 OC compared to its methyl esters at 120 OC. During this study it was
observed that for oil sample 50% weight loss was occurred at around 420 OC , while in case of methyl
esters it was around at 280 OC. All the volatile components of the oil which accounted for almost 90%
weight were decomposed at around 440 OC, whereas in case of respective methyl ester 90% weight
loss was observed at 295 OC. The remaining 10% was pyrolysis product which is highly viscous
liquids, under goes secondary decomposition. The temperature for secondary decomposition extended
up to 470-530 OC for oil and 320-380 OC for methyl esters. The residue was completely burnt out after
heating up to 700 OC for both oil and methyl esters. The above data confirms that oil is more thermally
stable and less volatile as compared to methyl esters. Further it is also confirmed that methyl esters
shows close proximity with conventional diesel.

3.5. Oxidative stability of Castor oil and methyl esters
         Oxidative stability is the quality indicative parameter for methyl esters. It is defined as the
resistance of the oil against oxidation.




            Fig.3- TGA profile of castor oil and methyl esters under oxygen environment


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        The consequence of lipid oxidation results in decreasing the shelf life of the oil. The oxidation
of long chain methyl esters initially results in accumulation of hydro peroxides. Then gradually it
polymerizes forming insoluble sediments that plugged filters, fouled injectors and interfered with
engine operation [15]. To measure the oxidative stability of the oil as well as methyl esters TGA
analysis was performed in air atmosphere under same conditions. During the analysis it was observed
that the onset temperature of oxidative degradation for oil sample was 230 OC, whereas, in case of
methyl esters it was 120 OC. That is mainly because methyl esters are less viscous than oil. This low
viscosity increases the contact between oxygen and ester molecules resulting higher oxygen diffusion
[29]. The vegetable oil contains naturally occurring antioxidants such as tocopherols, sterols and
tocotrienols, but the purification process destroys these natural antioxidants and hence becomes prone
to oxidation [30]. The oxidative stability of methyl ester can be improved either by using synthetic
antioxidants which are available in market or vegetable oil based antioxidant additives. So, further
research and development on castor oil based biodiesel will make it more attractive to replace fossil
fuels.

4. CONCLUSIONS

         Current investigation on the oil content and fuel properties of castor oil provides valuable
information on potential resources for biodiesel production. Physicochemical characterization of oil
and methyl esters established the suitability of the biodiesel to use in diesel engine. The castor oil
used in the present study showed low level of FFA, therefore single step alkali catalyzed
transesterification was found to be sufficient for biodiesel production. From the study it can be
concluded that castor oil can be used for large scale propagation and cost-effective biodiesel
production. However, more extensive and experimental study needs to be carried out to investigate
combustion, emission characteristics and its performance on Engine. Therefore, we still need to focus
on the process design, and kinetics of castor oil transesterification in a batch reactor and analysis in
biodiesel- fueled engine to establish castor biodiesel as successful alternative fuel.

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