preparation and characterization of biodiesel from karanja (pongamia pinnata) oil by different...

8/13/2019 PREPARATION AND CHARACTERIZATION OF BIODIESEL FROM KARANJA (PONGAMIA PINNATA) OIL BY DIFFERENT METHODS

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room temperature and reaction product was washedwith hot water until clear water found. The organic

phase was collected and dried under vacuum at 1000C for 30 min.

2.3.3. Three-step methodIn this method the raw oil was saponified, acidifiedand esterified sequentially [10]. Saponification wascarried out by different stoichiometric amount ofaqueous calcium oxide solution at 100 0C fordifferent time. The reaction time and molar ratio ofoil to calcium oxide were optimized. Aftersaponification, the soap solution were treated withdifferent stoichiometric amount of concentratedhydrochloric acid at a temperature of 60 -70 0C withvigorous stirring. After dissolving the soap, the FFAcontents were separated in separatory funnel. TheFFA content was determined by titrimetric method.Esterification of FFA was carried out as similar thefirst step of the two-step method. In esterificationreaction silica gel was used to adsorb water producedin esterification reaction, hence increase the reactionrate. The molar ratio of FFA to methanol, catalystconcentration and reaction temperature wereoptimized. The biodiesel was washed by hot waterand dried under vacuum at 100 oC temperature.

2.4. Analytical Methods for Oil and BiodieselFFA in the oil and biodiesel samples was analyzed bythe method described in AOCS Aa 6-38 [12]. Todetermine FFA of sample, 4-5 gm of samples weredispersed in isopropanol (75 mL) and hexane (15mL) followed by titration against 0.25 N NaOH.

Saponification value (SV) was determined by themethod described by Jeffery et al [13] . To determineSV 1gm sample was taken with 25 mL alcoholicKOH, heated for one hour in a steam bath withoccasional shaking and titrated the excess KOH withthe 0.5 M hydrochloric acid. The iodine value (IV)were determined by titrating 0.01 N sodiumthiosulfate to the mixture of tested fuel and chemicalreagents until the disappearance of the blue color

based on the analysis methods of American OilChemists Society. IV was calculated by thefollowing Eq. 1:

Iodine value = (B-S) x N x 0.001269 /W 1

Where, S and B are the amounts (in unit of mL) ofsodium thiosulfate titrated for the tested sample and

blank sample, respectively; N is the molarconcentration (in unit of mol/L) of sodiumthiosulfate; and W is the weight (in unit of g) of thetested sample. Cetane index (CI) was calculated byfollowing equation [14]:

CI = a +

+ cy 2

Where, x is the saponification value, y is iodinevalue a, b, c are constants. Here, a, b, c wascalculated by using the above equation for palm,

peanut and soybean oil fatty acid methyl estersrespectively.Physical properties such as moisture content anddensity of the oil were determined by followingASTM D 1744 (Karl fisher method), ASTM D1480/81 and ASTM D 240 respectively. Viscosity,flash point, pour point and cloud point weredetermined by standards ASTM D445, ASTM D 93(Pensky-Martens Flashpoint Apparatus, LazerScientific Inc, Germany), ASTM D 2500 and ASTMD 97 respectively.

3. RESULT AND DISCUSSION3.1. Extraction and Characterization ofKaranja Oil

The oil was extracted from Karanja seed by differentmethods and the oil content in the seed were 10.8(wt/wt) % and 23.4 (wt/wt)% found by press methodand sox let extraction method respectively.The properties of extracted karanja oil was measured

by standard method and presented in Table 1.

Table 1: Properties of karanja oil.

*Molecular weight was determined from compositionof the oil.

3.2. Preparation of Biodiesel3.2.1. Biodiesel Preparation by Acid

Catalyzed Transesterification reactionThe properties of biodiesel produced by acidcatalyzed transesterification reaction are presented inTable 2. Viscosity and FFA content of thetransesterification reaction product is higher than the

biodiesel standard due to its higher FFA content inthe raw oil. The acid catalyzed single step process istime consuming and even after 18 h the viscosity ofthe biodiesel is not comparable with the standard

biodiesel viscosity.

Property ValueSpecific gravity, at 25 C 0.97

Kinematic viscosity (mm2/s ), at 40 C 64

FFA content (%) 12.1

Moisture content (%) 0.08Saponification value (mg of KOH/gm

of oil)193.5

Cetane Index 54.5Iodine value ( g I 2/100 g oil) 83.8

Odor Mild flavor Color Dark brown

Molecular Weight (gm/mol) 889.1


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3.2.2. Biodiesel Preparation by Two-stepMethodsBiodiesel was prepared from karanja oil by two-stepmethod. In the first step (acid catalysed esterification)FFA was reduced with time. The FFA reduction was

presented in Figure 1. From the figure it wasobserved that after 2 h the FFA remain less than 2%.

0 15 30 4 5 60 75 9 0 1 05 1 20

3

6

9

12

% F

F A

T i m e ( m i n )

Fig. 1: Reduction of FFA in acid catalyzedesterification reaction [Reaction temperature = 60 0C,Methanol to oil molar ratio 5:1, and catalystconcentration 2 wt% of oil under reflux withvigorous stirring].

After the esterification reaction the product wassubjected to acid catalyzed transesterificationreaction. Acid catalyzed transesterification requires 6h instead of 2 h reported by Zullaikh et al. The

properties of biodiesel produced by two-step methodsare represented in Table 2. The viscosity and FFAcontent of produced biodiesel by tow-step method

was slightly higher than biodiesel standard but this process is also time consuming.

Table 2: Properties of biodiesel produced by acidcatalyzed transesterification and two-step method

Property Biodiesel produced by Acid

catalyzedtransesterification

method

Biodiesel produced by

Two-stepmethod

Color Radish-black Radish-black Viscosity

(mm 2/s) at 40 0C12.8 6.7

Saponificationvalue (mg

KOH/gm oil)

39.20 155.5

FFA (wt%) 2.2 1.5Specific gravity 0.93 0.93.2.3. Three-step method for biodieselPreparationOil was converted to FFA by saponification of oilfollowed by acidification mentioned above. The

results are represented in Figure 2. From Figure 2, itcan be seen that the optimum molar ratio of oil tocalcium oxide was 1:2 and reaction time was only 1h. Further increase in the molar ratio of oil to calciumoxide and reaction time, the conversion of oil to soapremain unchanged.

0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 00

20

40

60

80

10 0

% F

F A

T i m e ( m i n )

O i l : C a O = 1 : 2 O i l : C a O = 1 : 3

Fig. 2: Preparation of FFA from karanja oil throughsaponification and acidification by different

stoichiometric molar ratio of calcium oxide to oil inaqueous solution [Reaction temperature = 100 0Cunder reflux with vigorous stirring].

FFA obtained from oil was subjected to esterificationreaction to convert biodiesel. The reaction wascarried out with different FFA/methanol molar ratioin presence of acid catalyst (H 2SO 4). Effect ofFFA/Methanol molar ratio was investigated at 60 0Cand 5 wt% of catalyst. The maximum conversion ofFFA to methyl ester was found for FFA/ methanolmolar ratio of 1:9 after 2 h. At optimum molar ratioof FFA to methanol the FFA conversion was 94.2%

and 5.8 wt% FFA remain in the biodiesel. After prolonged reaction time could not reduced the FFA todesired level. In order to eliminate this problem, theesterification reaction was carried out in presence ofsilica gel. It was found that the presence of silica gelincreased the rate of reaction and the final FFAconversion was 99.05% by using 5 gm silica gel in 50gm FFA. Further increase in molar ratio of alcohol toFFA and silica gel the conversion of FFA andviscosity remain unchanged. The results are

presented in Figure 3.Effect of Catalyst Concentration was studied atFFA/methanol molar ratio of 1:9 at 60 0C in presenceof silica gel and the results are presented in Fig. 4.Fig 4 shows that 99.05% conversion of FFA can beachieved by 5 wt% catalyst (H 2SO 4) concentration.Further increase in catalyst concentration has noeffect on FFA conversion.


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2 4 6 8 10 120

2

4

6

8

10

12

% F

F A R e m a

i n i n g

Molar ratio of FFA to Alcohol

Esterification Reaction without silica gel Esterification Reaction with silica gel

Fig. 3 : Conversion of FFA to biodiesel at differentFFA/ methanol molar ratio in absence and presenceof silica gel [Reaction temperature = 60 0C, Catalyst(H 2SO 4) concentration 5.0 wt % of FFA and Reactiontime 2 h under reflux with vigorous stirring].Effect of temperature on esterification reaction wasstudied. The results are presented in Fig 5. It can beseen that the temperature has a significant effect onthe conversion of esterification reaction. As thetemperature increased, the conversion was alsoincreased. Figure 5 shows that 99.05% conversion ofFFA can be achieved at 60 0C. Further increase intemperature has no impact on FFA conversion.

0 2 4 6 80

5

10

15

20

25

30

35

40

45

50

55

% F

F A R e m a

i n i n g

Catalys t (wt% to FFA)

Fig. 4: Effect of catalyst (H 2SO 4) concentration onesterification reaction [Reaction temperature = 60 0C,FFA / methanol ratio 1:9 and Reaction time 2 h underreflux with vigorous stirring ].

3 0 4 0 5 0 6 0 7 00

2

4

6

8

% F

F A R e m a i n

i n g

T e m p e r a t u re ( 0 C )

Fig. 5: Effect of Temperature on esterificationreaction [Catalyst concentration 5 wt% of FFA, FFA/ methanol molar ratio 1:9, Reaction time 2 h underreflux with vigorous stirring].3.4 Optimum parameters for three-stepmethodsThe optimum reaction parameters for three-step

process are represented in Table 3.

Table 3: Optimum reaction parameters for three-step process

Step Parameters ValueSaponification Molar ratio of oil to

CaO1:2

Reaction Time 1.0 hAcidification Molar ratio of Soap

to HCl1:1.5

Esterification Molar ratio of FFAto Methanol

1:9

ReactionTemperature

60 0C

Catalyst (H 2SO 4)concentration

5 wt% toFFA

Reaction time 2.0 h

3.5 Properties of biodiesel produced bythree-step methodBiodiesel was prepared from karanja oil at optimumreaction condition and the properties of produced

biodiesel such as viscosity, density, flash point, cloud point, pour point, calorific value, FFA content,copper strip corrosion etc. are measured and shown inTable 4. Physical properties of biodiesel werecompared with standard biodiesel properties. All ofthe measured values were in the range of standard

biodiesel values.

4. CONCLUSIONBiodiesel has been prepared from karanja oil by acidcatalyzed transesterification reaction, two-stepmethod and three-step methods. Among thesemethods transesterification is best because it requiresfewer amounts of equipment and investment. But

base catalyzed transesterification is not used for the preparation of biodiesel from karanja oil because ofits high FFA content. Acid catalyzedtransesterification reaction was done for the

preparation of biodiesel. The viscosity of oil reducesfrom 64 mm 2/s to 12.8 mm 2/s and FFA reduces from12.1% to 2.2% after 18 h of reaction. The productwas not used as biodiesel because of its higherviscosity and FFA content and the process was timeconsuming. Acid catalyzed two-step method was

performed for the preparation of biodiesel. In acid

catalyzed esterification and transesterification theviscosity oil reduces from 64 mm 2/s to 6.7 mm 2/s andFFA of the oil reduces from 12.1% to 2.2%. Thevalue of FFA and viscosity are slightly higher than

biodiesel standard and the reaction was timeconsuming.Three-step method, where FFA was produced bysaponification and acidification of oil and thereafter

biodiesel was produced by esterification of FFA. Thereaction parameters such as temperature, molar ratio


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of FFA to alcohol and catalyst concentration wereoptimized.Hence three-step method can be used for biodiesel

production from karanja oil.Biodiesel properties was measured by standardmethods and compared with the standard biodiesel

properties. The copper strip corrosion test showednon corrosive nature of the biodiesel, it can be safelyused in the diesel engine.

Table 4: Properties of biodiesel produced by three-step method.

Properties Experimental value

BiodieselStandard[15, 16]

DieselStandard[16]

Viscositymm 2/s at 40 0C

4 1.96.0 1.3 4.1

SpecificGravity at 25

0C

0.889 0.88 (at15.5 0 C)

0.85 (at15.5 0 C)

Flash point(0C)

180 100 to170

60 to 80

Cloud point(0C)

12 -3 to 12 -15 to 5

Pour point(0C)

9 -15 to 10 -35 to -15

FFA (wt%) 0.95 - -

Copperstripcorrosion

Non-corrosive

- -

CalorificValue(Mj/Kg)

39.8 - 42

Saponificatio

n value (mgof KOH/gm

of oil)

143.24 - -

Iodiene value 92 - -

Cetane Index 63.70 - -

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6. NOMENCLATURESymbol Meaning Unit

N Normality Equivalent mol/L

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