of time on acid catalyzed and base catalyzed reaction.The conversion of karanja oil was found to be 99.5% under the optimized conditions of 1.0 wt % KOH and ...
International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 10, October 2014)
Effect of the Variation of Reaction Parameters and Kinetic Study for Preparation of Biodiesel from Karanza Oil Debarpita Ghosal1, Ranjan R. Pradhan2 1
2
Assistant Professor, Associate Professor, Department of Chemical Engineering, C.V. Raman College of Engineering, Bhubaneswar, Orissa, India
Abstract— The preparation of biodiesel from Karanja Oil using base catalyzed trans-esterification has been conducted and effect of variation of different process parameters like temperature, catalyst to oil ratio, catalyst concentration, effect of time on acid catalyzed and base catalyzed reaction.The conversion of karanja oil was found to be 99.5% under the optimized conditions of 1.0 wt % KOH and 6:1 methanol oil molar ratio at 65oC for a reaction period 45 mins.The kinetic study was carried out .The rate constants and activation were found from this
II. MATERIALS AND EXPERIMENTAL TECHNIQUES 2.1 Materials Karanja oil, Potassium hydroxide (KOH), Concentrated sulphuric acid (H2SO4), Methanol (CH3OH), n-hexane (C8C6), di-ethyl ether, ethyl acetate,. All solvents and chemicals obtained were used without any further purification. 2.2 Characterization of oil The properties and characteristics of Karanja oil were studied. Different properties like density, flash point, cloud point and pore point, acid value were evaluated for Karanja oil.
Keywords—Karanja Oil, biodiesel, kinetic study, fuel properties.
I. INTRODUCTION The increasing prices of petroleum and the growing environmental concerns caused by fossil fuel depletion has lead to the researchers to look for alternative fuel from renewable resources .Poratbility, ready-availability, renewability, higher combustion efficiency, lower sulphur and aromatic content, higher cetane no and higher biodegradability were the advantages of biodiesel as diesel fuel [1-6]. However, the use of edible oils for biodiesel production competes with its use as a food resource for human beings. The demand for vegetable oils for food has increased tremendously in recent years. It was impossible to justify the use of vegetable oils for fuel purpose such as biodiesel production. Moreover, vegetable oils were more expensive to use as fuel thus finding cheaper resources for biodiesel production is a challenging work to be done [7-13].This trans-esterification reaction can be carried out under supercritical conditions [14] The transesterification reaction process is the reaction of the oil or fat with an alcohol in the presence of suitable catalyst. In acid oils, the amount of free fatty acid could vary from 3-40% .When the amount of FFA in the oil exceeds 0.5%.the use of conventional alkali catalyst is not recommended due to the fact that the saponification reaction might take place [15-17].
Acid value: Acid value denotes free fatty acid content of oil. It can be defined as the amount of potassium hydroxide required for neutralizing 1g of karanja oil. It was carried out by titrating solution of Karanja Oil in neutral ethanol with 0.5(N) KOH. Phenlophthalein solution was used as an indicator for titration. Acid value was calculated using the following expression Acid value (mg KOH/g)=volume of titrant (in ml)× N × 56.10/Mass of the sample (mg) where N is the normality of accurately standardized sodium hydroxide solution. Density: The density of a material is defined as mass per unit volume. The density of the Karanja oil was determined at 25oC using specific gravity bottle according to ASTM D 4052 method. Density was calculated using the following expression. Density (kg/m3) =Mass (kg)/volume (m3) Kinematic Viscosity: Kinematic Viscosity is the measure of resistance of a fluid flow against gravity and is determined as the ratio of dynamic viscosity to the density. Dynamic viscosity was measured and kinematic viscosity was calculated using the following equation
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 10, October 2014) Kinematic Viscosity (m2/s) = Dynamic viscosity (pa.s or kg/m.s)/Density (kg/m3)
2.5 Base catalyzed trans-esterification: The pretreated oil was poured into the reaction flask and heated. The solution of KOH with methanol (1%) was also heated at 60 oC and the pre treated oil was added. The molar ratio of methanol to oil was 6:1.and the mixture was kept in stirring condition by glass stirrer. The reaction was stopped after 2 hr and the reaction mixture was poured to the separatory funnel. The lower layer containing glycerol and other impurities was drawn off. The upper layer of biodiesel was washed with lukewarm water to free the excess alkali present there. The biodiesel product was kept in a hot air oven at 110 oC for 1h to remove the moisture. For kinetic study, a definite volume of the reaction mixture was taken out by pipette time to time and analysed by Gas Chromatography. The effect of varying the parameters such as catalyst concentration (0.25, 0.50, 0.75, 1.0, 1.25 wt %), methanol to oil molar ratio (3:1, 6:1, 9:1 and 12:1), reaction temperature (15, 30, 45, 60, 65 oC), reaction time (15, 30, 45, 60 min) on the biodiesel yield was studied. GC consists of CHEMITO GC 8610 with flame ionization detector and nitrogen as carrier gas. Column was packed with BPX-70. Injection temperature was maintained at 250 oC and detector was at 260 oC.The oven temperature was maintained at 160oC. The result obtained was compared with standard methyl ester sample.
Cloud point and pour point: Cloud point is the maximum temperature at which the sample become hazy and pour point is the maximum at which it ceases to flow. The oil is taken in a pour point apparatus fitted with an alcohol thermometer and the temperature at which the oil ceased to flow was recorded as pour point of biodiesel. The temperature before the pour point at which the oil started becoming hazy is called the cloud point. The pour point was recorded at 5 oC. 2.3 Reaction set-up: The reaction set-up consists of a two necked round bottom flask of capacity 250 ml. The flask was assembled with a glass stirrer and a glass condenser. Total set-up was fixed inside a heating jacket with temperature controller to maintain the temperature 60oC with an accuracy ±1oC. Methanol has a boiling point of 65 oC.The water cooled condenser was fixed to prevent the loss of methanol during reaction. The condenser also helps to maintain the atmospheric pressure inside the reactor. The stirrer was introduced vertically within the reactor to make sure the mixing of the reactants effectively and with constant rate. 2.4 Acid catalyzed esterification process Base catalyzed transesterification process is very sensitive to the FFA content of Karanja Oil. The FFA content should be within 0.5-1% in Karanja Oil.Greater percentage of FFA leads to the deactivation of catalyst by forming soap and emulsion [Van Gerpen J.,Biodiesel Processing and production,Fuel Process Technology,2005:86:1097-107].Therefore FFA content should be minimized below 2mg/g of KOH by converting it into respective methyl ester. This pretreatment was done by reacting Karanja Oil with methanol in excess catalyzed by H2SO4. It has been already reported in literature that the sample of oil having acid values less than 2mg/KOH is used for base catalyzed reaction.[Sharma Y.C, Singh B, Upadhyay S.N., Advancements in development and characterization of biodiesel:a review,Fuel,2008;87: 235573]. Acid catalyzed reaction is the pre treatment procedure to decrease the acid value below 2mg/g of KOH. Esterification reaction was performed with methanol to oil volume ratio as 7:1.at 65O C with 1.8 wt% H2SO4 as catalyst. During the course of a reaction the FFA value was checked for the sample by withdrawing the sample time to time when the required FFA level was reached the mixture was cooled and kept overnight for settling without disturbing the mixture.
III. RESULTS AND DISCUSSIONS 3.1 Oil properties and characteristics Table I. Fuel Properties Of Karanza Oil Density (Kg/m3) Acid Value (mg KOH/g)
982 13.34
Kinematic Viscosity at 40 oC (cst)
28
Flash Point (oC)
235
Fire Point (oC)
251
Table II Fuel properties of biodiesel obtained from Karanza Oil:
311
Density (Kg/m3)
935
Distillation Temperature (oC)
356
Kinematic Viscosity at 40 oC (cst)
4.22
Flash Point (oC)
214
Fire Point (oC)
225
International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 10, October 2014) Physical and chemical properties of Karanza oil were studied by standard ASTM methods and the results were tabulated in Table I and Table II.
90 80
Conversion (%)
70
3.2 Effect of reaction time on acid catalyzed reaction Effect of reaction time on acid catalyzed esterification reaction is described in Figure 1.Initial acid value of raw Karanja Oil was found to be 13.34.The acid catalysis reduced the acid value from 13.34 to 1.8 stepwise, and then became constant. The acid value was observed to decrease in 50 minutes
60 50
40 30 20 10 0
0
0.5
1.5
Catalyst (wt%)
16 Acid Value(mg of KOH/mg)
1
14
Figure 2 Effect of catalyst amount on conversion
12
3.4 Effect of methanol to oil ratio One of the important variables in this trans-esterification reaction is methanol to oil ratio. The effect of this parameter on conversion of oil to biodiesel is shown in Figure 3. Initially the conversion was increased with increase in methanol to oil ratio. The experiments were carried out with the ratio 3:1, 6:1, 9:1, and 12:1.The experiments were conducted with 1% catalyst concentration, 55 oC reaction temperature, 30 mins of reaction time and 600 rpm stirrer speed .
10 8 6 4 2
0 0
20
40
60
80
100
Time (min)
Figure 1 Effect of reaction time on acid catalyzed reaction 90
3.3 Effect of catalyst It was observed from literature that the required amount of alkali is 1% or less than that to complete the reaction. The effect of catalyst amount on base catalysed transesterification of Karanja oil is shown in Figure 2.The conversion was increased with increase in amount of catalyst KOH upto 1%. The optimum amount of catalyst 1%.There was no alteration could be seen beyond 1% catalyst concentration. The reaction conditions are as follows: Methanol:Oil - 6:1, Reaction Temperature-55 oC, Reaction Time- 30 min
Conversion (%)
80 70 60 50 40 30
20 10 0 0
3
6
9
12
15
Methanol:oil
Figure 3 Effect of methanol to oil ratio on conversion
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International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 10, October 2014)
Conversion (%)
3.5 Effect of temperature on conversion The effect of temperature on conversion was carried out by conducting the experiment at 5 different temperatures with 1% catalyst concentration, methanol to oil ratio 6:1 and 30 minutes of reaction time. The result is graphically represented in Figure 4.
The overall reaction was assumed to be single step reaction. Kinetic rate constant was established using the model, ignoring the intermediate steps the overall reaction could be written as TG +3CH3OH = 3RCOOCH3 + Glycerol According to the reaction mentioned the rate equation can be represented as
100 90 80 70 60 50 40 30 20 10 0
Rate = - d [TG]/dt =k [TG] Integrating the above equation by taking that the initial concentration of TG at time t=0 as TG0 and concentration at time, t =t as TG [Smith JM, Chemical Engineering Kinetics, 3rd ed. New York: Mc-Graw-Hill International] -∫d [TG] = k ∫dt 40
45
50
55
60
65
-ln ([TG]/TG0]) = kt
70
The rate constants and the R2 values are tabulated in Table III.It can be seen from the table that the first order kinetic model appears to be the best model for this reaction. Rate constants are sensitive to temperature and increases with increase in temperature. The rate of the reaction increases with increase in temperature for elementary reactions. From the observation it can be said that the assumption of irreversible reaction was agreeable.
Temperature (oC)
Figure 4 Effect of temperature on conversion
It can be seen from figure 4 that the conversion was increased with increase in temperature and the optimum temperature was found to be 60 oC beyond that point no change was observed with increase in temperature. 3.6 Effect of time on conversion Figure 5 shows the effect of time on conversion. The experiment was carried out and samples were collected at time intervals ranging from 15-60 min. The optimum conversion of 99.5% was observed.
Table III Rate Constants And Different Temparatures For Trans-Esterification Of Karanja Oil Temp (oC)
Rate Constant ,k
R2 values
(/min)
95
Conversion (%)
90 85
45
0.012
0.99
55
0.056
0.96
65
0.138
0.97
80 75
70 65 60 0
20
40 Time (min)
60
80
The rate constant with respect to temperature was used to determine activation energy by Arrhenius equation. K = Ae-Ea/RT Figure 5 Effect of time on conversion
After integration
3.7 Kinetic Modelling The proposed mechanism based upon homogeneous catalytic reaction. This reaction follows a first order kinetics as a function of the concentration of oil (Triglyceride [TG]) and the reaction temperature..Due to the high methanol concentration it cannot be taken as limiting agent.
Lnk =lnA (–Ea/RT) Where A is frequency factor Ea is activation energy in cal /mol, R =1.987 Cal/Mol. and T is temperature in K. The activation energy was estimated by plotting lnk vs 1/T. This result proves the first order kinetics. 313
International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 10, October 2014) [6]
The activation energy was calculated to be 25220.99cal/mol which is almost similar with the literature.
[7]
IV. CONCLUSION The Karanja oil was successfully converted to biodiesel which met the specification of biodiesel standard and fuel specification with ASTM standard and standard published literature. The two step process of combined acid and then base catalyzed transesterification for the production was discussed The effect of different process parameters was studied.The kinetic study of the bease catalysed transesterification was also studied successfully.The activation energy calculated from the study found similarity with the previous literature.
[8]
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