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Ultrasound assisted intensified production of biodiesel from sustainable source as karanja oil using interesterification based on heterogeneous catalyst (γ-alumina)
Accepted Manuscript Title: Ultrasound assisted intensified production of biodiesel from sustainable source as karanja oil using interesterification based on heterogeneous catalyst (␥-alumina) Authors: Shubham S. Kashyap, Parag R. Gogate, Saurabh M. Joshi PII: DOI: Reference:
S0255-2701(18)31223-6 https://doi.org/10.1016/j.cep.2018.12.006 CEP 7444
To appear in:
Chemical Engineering and Processing
Received date: Revised date: Accepted date:
8 October 2018 26 November 2018 13 December 2018
Please cite this article as: Kashyap SS, Gogate PR, Joshi SM, Ultrasound assisted intensified production of biodiesel from sustainable source as karanja oil using interesterification based on heterogeneous catalyst (␥-alumina), Chemical Engineering and Processing - Process Intensification (2018), https://doi.org/10.1016/j.cep.2018.12.006 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Ultrasound assisted intensified production of biodiesel from sustainable source as karanja oil using interesterification based on heterogeneous catalyst (γ-alumina)
Shubham S. Kashyap, Parag R. Gogate*, Saurabh M. Joshi.
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Department of Chemical Engineering, Institute of Chemical Technology, Matunga,
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Mumbai, India-400019
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*Correspondence should be addressed
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Email: [email protected]
Graphical-abstract
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Intensified Synthesis of Biodiesel using ultrasound assisted approach 80
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Yield (%)
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ultrasound
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conventional
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Highlights
First depiction of application of heterogeneous catalyst for intensified interesterification of karanja oil Understanding the effect of operating parameters for maximizing yields
Comparison of ultrasound assisted approach with the conventional stirring
Optimized conditions give about 40% higher product yield for ultrasound
Successful demonstration of the reusability of the catalyst
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Abstract
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Intensification of ultrasound (US) assisted interesterification of karanja oil in the presence of
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γ-alumina as a heterogeneous catalyst was performed in current study. Effect of reaction
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conditions as reactant molar ratio, catalyst loading, duty cycle and temperature on the yield of
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FAME has been investigated. The catalyst used in the work, γ- alumina, is an acidic catalyst and hence is resilient to high FFA and water content, making it as an efficient catalyst as no
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pretreatment is required even for karanja oil as sustainable feed stock. Optimum conditions established in the work for interesterification are 1 wt. % catalyst loading, duty cycle of 60
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%, reactant molar ratio of 1:9 and temperature of 50oC resulting in FAME yield of 69.3% in 50 min. Reusability studies also confirmed that γ-alumina can be reused for six cycles
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without much loss of activity. It was also demonstrated that conventional stirring based approach gave only 50.8% which is much lower than that obtained in the presence of ultrasound. The present study clearly demonstrated that use of ultrasound gives process intensification benefits and there are no negative effects on the γ-alumina used as catalyst as demonstrated by the reuse for six cycles.
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Keywords: Ultrasound; interesterification; γ- alumina; biodiesel; process intensification; sustainable feedstock
1. Introduction
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Throughout human history, use of different fuels with consistent improvisation in the nature
mostly with an objective of enhanced efficiency and lower emissions has always been the
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practice. Earlier in the agrarian era, wood was burned for warmth and cooking and with the invention of steam engines, agrarian economy turned into industrial economy. Steam engines
could be fuelled by both wood and coal. Coal was quickly accepted as a preferred fuel as it
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produced four times energy as produced by same amount of wood. In 20th century,
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technological advancements changed the focus from coal to oil. Refined oil products (petrol
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and diesel) have been in use to power various industries and automobiles, but these are nonrenewable energy resources and also many a times considered to be enhancing the
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atmospheric pollution. Limited availability also makes them scarce and it is essential to seek for some alternative resources. Biodiesel is one of the commercially accepted alternatives for
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non-renewable energy resources available today [1]. Biodiesel can be produced from vegetable oil, animal fat or waste oil mostly based on conversion to alkyl esters [2]. It is
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commonly produced by transesterification of triglycerides and methanol with glycerol as byproduct and requires subsequent separation and purification [3,4]. Though the method is
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commonly used, higher costs of production and generation of the low value product as glycerol has been the major concerns for production. An alternative is the process of interesterification in which alkyl acetate is used instead of alcohol as acyl acceptor group and triacetin is obtained as a byproduct instead of glycerol. Triacetin has more value as compared to glycerol as it is used as solvent and plasticizer and can also be left in product mixture as
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fuel component. Up to 10 wt. % triacetin in biodiesel is allowed as per the ASTM D6451 and EN 14214. Considering these advantages, the present work has focused on interesterification of karanja oil (as a sustainable feed stock). The synthesis processes of interesterification can be catalyzed by acidic, basic or enzymatic catalyst. Basic catalysts are not corrosive in nature but high free fatty acid (FFA) and water
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concentration leads to saponification reaction and hence the problems in processing. Acidic
catalysts are susceptible to water content and usually give lower rates of processing. Mostly
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homogeneous basic catalysts have been used in interesterification reaction using oil with low
FFA content as per the reports in the literature or a two stage esterification followed by
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interesterification has been applied. Homogenous catalysts are soluble in the reaction mixture
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and hence their separation is difficult unlike heterogeneous catalysts which can be recovered
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and reused easily. In the production of biodiesel, final cost is affected mainly by the cost of
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raw material and catalyst. Raw material cost can be reduced using sustainable feed stock (lower costs and no conflict with the main value chain) such as the different non-edible oils
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instead of the edible oils. Catalyst cost can be reduced by using heterogeneous catalyst because it can be effectively reused after easy separation and also the product purification
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step is easier so that the overall production cost reduces. Reusability is an important characteristic of heterogeneous catalysts which reduces the total cost for multiple batches.
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An analysis of the literature revealed that use of heterogeneous catalysts has mostly been only reported for the transesterification of oils. Saha and Goud [5] investigated the
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transesterification of karanja oil using heterogeneous base (Ba(OH)2·8H2O) catalyst in the presence of ultrasound and effect of concentration of catalyst, reaction time, temperature, and reactant molar ratio on the yield of biodiesel was studied. It was reported that maximum of 84% conversion is obtained under optimized operating conditions. Kim et al. [6] prepared Na/NaOH/γ-Al2O3
heterogeneous
base catalyst
and investigated
its
use in the
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transesterification of soy bean oil to biodiesel demonstrating a yield of 94% under optimum conditions. Ribeiro et al. [7] investigated the use of niobium phosphate, γ-alumina, zeolite HY and niobium oxide as the solid catalyst for the interesterification of macaw oil. It was reported that that among all the catalysts used, γ-alumina and niobium phosphate were reported to be most suitable with γ-alumina resulting in FAME yield of 52.5 % in 1 h and
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niobium phosphate requiring 2.5 h for 52.9 wt% as the yield of FAME. Gaikwad and Gogate
[8] synthesized a carbon based heterogeneous catalyst and investigated its application for
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biodiesel synthesis in the presence of ultrasound reporting a maximum of 77.4% of conversion at optimum conditions of 6:1 as the reactant molar ratio, 3 % by weight as the
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loading of catalyst, reaction time as 3 h, temperature as 333 K, ultrasonic power dissipation
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of 120 W and frequency of 20 kHz. Analysis of the literature revealed that there has been no
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report for the intensification of interesterification reaction catalyzed by heterogeneous
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catalysts and hence the present work deals with intensification of interesterification of karanja oil using ultrasound. The selection of karanja oil is justified based on the fact that earlier
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studies have used other sustainable feed stocks for biodiesel production as macaw oil [9] or waste cooking oil [10]. Srivastava and Verma [11] reported the synthesis of biodiesel from
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karanja oil but it was based on the transesterification reaction and intensification studies have not been reported. In summary the current work focuses on the use of karanja oil as a feed
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stock with γ-alumina as heterogeneous acidic catalyst. Ultrasound (US) as process intensification technique was also used in the work with comparison with the conventional
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stirring based approach. Cavities produced by ultrasound grow rapidly and implode on reaching a desired size with generation of micro jets and these micro jets further result in turbulence in the reaction mixture facilitating mass transfer with higher rates of reaction [12]. The current study also aimed at understanding the effects of operating parameters like
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catalyst loading, molar ratio (methyl acetate to oil), US duty cycle and temperature so as to maximize the effects of intensification.
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2. Materials and Method 2.1 Materials
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Karanja oil was procured from Svas Enterprise Pvt. Ltd, Mumbai with the detailed
composition mentioned in our earlier study [13]. Methyl acetate was obtained from S.D. Fine Chem. Ltd., Mumbai whereas acetone and acetonitrile (HPLC grade) were procured from Hi
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Media, Mumbai. γ- alumina, used as catalyst and methyl oleate and methyl linoleate
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standards used in HPLC analysis process were obtained from Sigma-Aldrich.
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2.2 Experimental setup
In the current study, US horn (Dakshin Pvt. Ltd.) was used as source used for ultrasonic (US)
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irradiation with 20 kHz frequency and 120 W power suitable for laboratory scale studies. US horn had a tip diameter of 11mm and was immersed in reaction mixture up to 20 mm. A
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round bottom glass reactor (diameter – 11 mm, capacity – 150 mL) equipped with 3 openings
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(used for sample withdrawal, temperature measurements, agitators or condensers as required) was used for reactions. Water bath was used to control reaction temperature with partial reactor immersion and stirring with help of magnetic stirrer. The overall reaction setup was
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similar as that described in our earlier study on interesterification using homogenous catalyst [13]. Condensation of evaporated methyl acetate vapors was controlled with a reflux condenser attached to vessel. Similar setup without US was used for the conventional approach in the presence of stirring. 2.3 Experimental Methodology 6
The interesterification reaction of karanja oil with methyl acetate was performed in the batch mode at reaction volume of 100 mL. The mixture containing the reactants in desired ratio was heated to the desired temperature and then catalyst was added to the reactor on achieving the required temperature and this point is considered as the start of the reaction. Effect of different operating parameters as catalyst loading (different values as 0.5, 1, 2 and 3% wt),
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duty cycle of ultrasonic horn (different values as 40, 50, 60 and 70%), oil to methyl acetate
molar ratio (OMAMR) (different values as 1:4, 1:9, 1:12 and 1:14) and temperature (different
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values as 30, 40 and 50 °C) on the yield of biodiesel from waste cooking oil has been investigated in the current work. Under the optimized set of operating parameters
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experiments were also performed using conventional approach without US to study degree of
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intensification obtained with US. Progress of the reaction was monitored with periodic
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withdrawal of samples at regular intervals. The withdrawn samples were first washed with hot water. Subsequently, the possible traces of water and methyl acetate were removed by
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heating the samples in crucibles at 150oC. The processed samples were subjected to the
2.4 Analytical method:
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HPLC analysis to estimate the yield of biodiesel.
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Analysis of FAME obtained after interesterification of karanja oil was performed using
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HPLC (Thermo Scientific Acclaim 120) equipped with a UV/visible detector operated at 205 nm and C-18 HPLC column (dimensions: 4.6 × 150 mm). Mobile phase (flow rate of 0.8 mL/min) used for analysis was a solution of acetonitrile and acetone in (70:30 v/v ratios) and
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it was used along with oil sample dissolved (10μL oil in 10mL solution) in the mobile phase for analysis. Amount of the FAME obtained was estimated on comparison of obtained peak areas of the standards (methyl oleate and methyl linoleate). Yield of biodiesel was calculated with the help of following equation:
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Yield of Biodiesel =
Total weight of methyl esters Total weight of oil used
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(1)
HPLC chromatogram obtained in the current work is shown in Fig.1. Presence of methyl linoleate and methyl oleate in the obtained sample can be confirmed based on the comparison of the peaks obtained at retention time of 8.5 min and 11.19 min respectively with the
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standard [13].
3. Results and discussion 3.1 Effect of catalyst loading on FAME yield
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Effect of catalyst loading on the yield of FAME has been investigated over the range of 0.5
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wt. % to 3 wt. %, keeping values of duty cycle (60%), reactant molar ratio (1:9) and
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temperature (50oC) as constant. Fig 2. depicts the obtained trends for the yield with changes
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in the catalyst loading and it can also be observed from the figure that yield increases from
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60.4% to 69.2% with an increase in catalyst loading from 0.5 wt. % to 1 wt. %. On increasing catalyst loading from 1 wt. % to 2 wt. %, increase in yield was marginal from 69.2% to 72%
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and on further increase in catalyst loading from 2 wt. % to 3wt. %, the yield decreased from 72% to 66.4%. The available number of active sites typically increases with an increase in
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catalyst loading, which results in higher yield initially till the optimum. A subsequent increase in amount of heterogeneous catalyst above optimum makes the reaction mixture too
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dense/viscous resulting in an incomplete dispersion. Increased viscosity is responsible for poor mixing and similar trend was also reported by Kim et al. [6] and hence a decrease in yield on increasing catalyst loading from 2 wt. % to 3 wt. % was observed in the present work. In the current study, an optimum value of catalyst loading of 1 wt. % has been established, while in literature for similar studies, higher loadings of catalysts is reported. Ribeiro et al. [7]
reported an optimum catalyst loading of 5 wt. % in the case of 8
interesterification of macaw oil with conventional stirring method using γ-alumina. Tian et al. [14] reported an optimum catalyst loading of 7.5% in the case of interesterification of triolein as model feedstock using ferric sulfate as heterogeneous catalyst while Gaikwad and Gogate [8] have reported an optimum catalyst loading of 3 wt.% in the case of ultrasound assisted esterification of PFAD using sulfonated carbon catalyst. The comparison with the literature
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has enabled to understand that the optimum catalyst loading is typically specific to the system
and need to be established as per the method reported in the work. It is very important to
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understand that lower optimum as established in the current work mean higher activity of the catalyst.
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3.2 Effect of duty cycle on FAME yield
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Different values of duty cycle ranging from 40% to 70% were used in the work to study the
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effect of duty cycle on FAME yield with values of catalyst loading (1 wt. %), reactant molar
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ratio (1:9) and temperature (50oC) being maintained as constant. Duty cycle decides time for
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which the US source is kept ON and OFF during reaction which further helps to achieve sufficient cooling of ultrasonic horn and also reduce the net power consumption. The results
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obtained for variation in yield with duty cycle depicted in Fig.3 confirm that yield increases from 54.3% to 69.3% with an increase in duty cycle from 40% to 60% which can be
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attributed to the fact that increasing duty cycle increases the cavitation activity which is responsible for increase in yield. A further increase in duty cycle from 60% to 70%, however,
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resulted in a decrease in the yield from 69.3% to 66.4%. Decrease in yield can be attributed to the fact that beyond an optimum value of duty cycle, excess of cavitation causes cushioning effect and lowers the cavitational intensity [15,16] Maddikeri et al. [16] reported similar trend for interesterification of waste cooking oil with 60% as the established optimum duty cycle. Joshi et al. [15] reported an optimum duty cycle of 70% for the transesterification of
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karanja oil whereas Subhedar and Gogate [17] reported an optimum duty cycle of 60% for the enzymatic interesterification of waste cooking oil. 3.3 Effect of reactant molar ratio on FAME yield Effect of reactant molar ratio on the yield of FAME was studied by changing the reactant
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molar ratio from 1:4 to 1:14 keeping the values of catalyst loading constant as 1 wt. %, duty cycle as 60%, and temperature as 50 oC as constant. The obtained trends for the change in
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yield with reactant molar ratio presented in Fig. 4 establish that FAME yield increases from 36.5% to 69.3% with an increase in reactant molar ratio from 1:4 to 1:9 which can be attributed to the fact that increase in concentration of reactants increases the rate of forward
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reaction as interesterification is a reversible reaction [17]. Yield was observed to decrease
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further with an increase in reactant molar ratio beyond the optimum and at 1:14 molar ratio,
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yield was only 58.7%. Similar study on interesterification reported optimum reactant molar
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ratio of 1:12 with 90 % biodiesel yield [16], while Subhedar and Gogate [17] reported an
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optimum reactant molar ratio of 1:9 in the case of ultrasound assisted interesterification of waste cooking oil using immobilized lipase as catalyst. In the case of interesterification of
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triolein using ferric sulfate as heterogeneous catalyst by conventional stirring method, similar trend has been reported but with a requirement of higher reactant molar ratio as 1:20 [14]. In
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another study by Casas et al. [18], 1:48 molar ratio was reported as the best condition in the case of interesterification of sunflower oil using potassium methoxide. Hence it can be said
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that optimum requirement of methyl acetate depends on the specific system in question and hence, importance of current work is established. 3.4 Effect of temperature on FAME yield Experiments were conducted to study the effect of temperature variation on yield of FAME with variation in the temperature from 30oC to 50oC keeping constant values of catalyst 10
loading as 1 wt. %, duty cycle as 60% and reactant molar ratio as 1:9. The obtained data for the yield at various temperatures Fig.5 confirmed that with an increase in temperature from 30oC to 40oC, the yield increased from 48.5% to 62.9% which can be attributed to the fact that higher temperature helps in overcoming the energy barrier with supply of required amount of energy. Miscibility of methyl acetate and oil also increases helping the reaction to
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proceed at faster rate. On further increase in temperature from 40oC to 50oC, increase in the yield was only from 62.9% to 69.3% possibly due to reduction in extent of cavitation activity.
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Higher temperature significantly reduce viscosity and surface tension of liquid which is responsible for reduction in cohesive forces within the liquid and energy required to tear
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apart, thus making cavitation much easier. High temperature also increases the presence of liquid vapors which further produces vaporous cavities leading to cushioning effect during
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compression cycle affecting activity of cavitation. Temperature of 50 oC was considered to be
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the best operating temperature in current study as there was still an increase in the yield (by about 7%) and higher temperatures were not tried in the work due to the boiling point of one
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of the reactants as well as problems with lower cavitational efficiency. Maddikeri et al. [16] also reported similar results for the interesterification of waste cooking oil with optimum
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temperature of 50oC.
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3.5 Kinetic analysis:
Integral analysis was also performed for second order fitting using conversion vs. time data. Fig. 6 shows the data fitting for the second order kinetics at different temperatures of 30oC,
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40oC and 50oC. The reaction kinetics was found to fit well in second order mechanism similar to the literature reports by Maddikeri et al. [16] and Casas et al. [18] in the case of waste cooking oil and sunflower oil respectively. Values of rate constants along with correlation coefficient (R2) are presented in Table 1. Rate constants are found to increase from 0.16 to 0.36 L/mol with an increase in temperature from 30 to 50 oC. Similar trend was reported by 11
Maddikeri et al. [16] in the case of interesterification of waste cooking oil in the presence of ultrasound with an increase in the rate constant from 0.22 to 0.93 (L/mol min) for an increase in temperature from 30oC to 50oC. Activation energy was obtained from plotting data of rate constant and temperature (Fig.7)
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and was calculated to be 32.68 kJ/mol. The work of Maddikeri et al. [16] reported higher activation energy as 58.17 kJ/mol. The comparison establishes the ease of reaction for the
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karanja oil under the processing conditions used in the current work. 4. Comparison of acoustic cavitation with conventional stirring
For conventional process with stirring, optimized parameters (catalyst loading of 1 wt. %,
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reactant molar ratio of 1:9 and temperature of 50 oC) were employed. Comparison of yield
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obtained by ultrasound assisted approach and conventional method under reported optimized
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conditions is presented in Fig. 8. It can be observed from the figure that biodiesel yield
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increased by almost 40 % for ultrasonic assisted technique (actual value of 69.3%) on
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comparison with conventional method (actual value of 50.8%). Literature available on reactions performed conventionally with mechanical stirring also show that such reactions
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don’t give high yield and take more time in comparison to those assisted with ultrasound. Ribeiro et al. [7] reported yield of 52.49% in 1 h for interesterification of macaw oil using γ-
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alumina with conventional stirring method while Tian et al. [14] reported a yield of 75% in 12 hours in the case of interesterification of triolein using ferric sulfate. Study of enzymatic
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interesterification of crambe oil assisted by ultrasound [19] revealed that 38.7 % yield is obtained in 2 h of reaction with US and less than 10% is obtained even after 10h of reaction for conventional process. The reported results suggest that ultrasound accelerates the reaction rate and also reduces the requirement of enzyme compared to reaction without ultrasound. Major problem with conventional stirring method for interesterification reactions is improper mixing because oil is immiscible with methyl acetate. Ultrasound causes cavitation which 12
produces micro jets, local turbulence and micro emulsions which overcomes the problem of mixing and enhances the available interfacial area for the reaction.
5. Reusability of catalyst Reusability is one of the most important characteristic of heterogeneous catalyst as its
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separation from the reaction mixture is easier as compared to homogeneous catalyst. In first run, fresh catalyst was used which was recovered and reused in seven consecutive runs to
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evaluate reusability of γ-alumina. The obtained results shown in Fig.9 established that after
the second cycle, FAME yield decreases marginally from 69.25% to 69% which is not
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significant. In the sixth cycle, the yield decreased to 63.71% whereas in seventh cycle, yield
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was found to be 60%. The reduction in yield can be attributed to the loss of catalyst in the recovery process and reduction in its activity after every run. Ribeiro et al. [7] reported
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reusability of five times for γ-alumina in the case of interesterification of macaw oil with conventional stirring method with 9.1% reduction in yield. In the current study, it was
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observed that with assistance of ultrasound made γ-alumina to be used for six times with only 7.9% reduction in yield. Comparing to conventional stirring method, γ-alumina with
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assistance of ultrasound performed better in terms of reusability attributed to the fact that ultrasound generates microscale cavities which collide and collapse on catalyst surface and
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thus clean the catalyst surface mechanically and help in regeneration. Hence it can be said
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that use of ultrasound increases the reusability of heterogeneous catalyst.
6. Conclusions In the current study, ultrasonic irradiation was demonstrated to be an efficient method for interesterification of karanja oil using heterogeneous catalyst. Ultrasound assistance resulted in significant increase in yield from 50% to 70% as compared to conventional stirring based
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method. The optimum parameters obtained were 1 wt. % as catalyst loading, 60% as duty cycle, 1:9 as reactant molar ratio and 50oC as temperature. Microscale cavities generated by ultrasound collide and collapse on catalyst surface with increased regeneration of catalyst and higher reusability of catalyst. In the current study γ- alumina was successfully reused for 6 cycles with no significant loss of activity. Overall, the most importance finding of the study is
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that heterogeneous catalyst, γ-alumina, resulted in almost 70 % FAME yield from karanja oil
with no requirement of esterification process and easy separation from reaction mixture with
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subsequent reuse.
A.E. Atabani, A.S. Silitonga, I.A. Badruddin, T.M.I. Mahlia, H.H. Masjuki, S.
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esterification of karanja oil for production of biodiesel with optimization using response surface methodology, Chem. Eng. Process. Process Intensif. 124 (2018) 186– 198. [16] G.L. Maddikeri, A.B. Pandit, P.R. Gogate, Ultrasound assisted interesterification of waste cooking oil and methyl acetate for biodiesel and triacetin production, Fuel
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Figure Caption
Fig. 1 HPLC Chromatogram of biodiesel sample. Fig. 2 Effect of catalyst loading on the yield of biodiesel at constant duty cycle of 60%,
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reactant molar ratio of 1:9 and temperature 50oC.
reactant molar ratio as 1:9 and temperature 50oC.
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Fig. 3 Effect of duty cycle on the yield of biodiesel at constant catalyst loading of 1 Wt. %
Fig. 4 Effect of reactant molar ratio on the yield of biodiesel at constant catalyst loading of 1
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Wt. %, duty cycle of 60% and temperature at 50oC.
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Fig. 5 Effect of temperature on the yield of biodiesel at catalyst loading of 1 Wt. %, duty
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cycle as 60% and reactant molar ratio of 1:9.
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Fig. 6 Kinetic study for establishing the rate constants of US assisted interesterification
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process.
Fig. 7 Arrhenius plot for estimation of activation energy.
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Fig. 8 Comparison of biodiesel yield in the ultrasound assisted and conventional method with stirring at optimized parameters as 1 wt. % catalyst loading, 60% duty cycle, 1:9 as reactant
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molar ratio and 50oC temperature. Fig. 9 Study of γ-alumina reusability in interesterification reaction of karanja oil and methyl
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acetate.
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Fig. 1 HPLC Chromatogram of biodiesel sample.
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80 70
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0.5 Wt%
30
2 Wt%
50 40
1 Wt%
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Yield (%)
60
3 Wt%
20
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10 0
0
10
20
30 Time (min)
40
50
60
Fig. 2 Effect of catalyst loading on the yield of biodiesel at constant duty cycle of 60%, reactant molar ratio of 1:9 and temperature 50oC.
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80 70
50 40%
40
50%
30
60%
20
70%
10 0 10
20
30 Time (min)
40
50
60
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0
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Yield %
60
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reactant molar ratio as 1:9 and temperature 50oC.
80
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70
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60 50 40
1:4 1:9
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Yield (%)
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Fig. 3 Effect of duty cycle on the yield of biodiesel at constant catalyst loading of 1 Wt. %
30 20
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10
1:12 1:14
0
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0
10
20
30 Time (min)
40
50
60
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Fig. 4 Effect of reactant molar ratio on the yield of biodiesel at constant catalyst loading of 1 Wt. %, duty cycle of 60% and temperature at 50oC.
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80 70
50 40
30C
30
40C 50C
20 10 0 2
4
6 Time (min)
8
10
12
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0
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Yield (%)
60
Fig. 5 Effect of temperature on the yield of biodiesel at catalyst loading of 1 Wt. %, reactant
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2.5
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2
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1.5
1
30C 40C 50C
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X/(1-X)
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duty cycle as 60% and molar ratio of 1:9.
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0.5
0
2
4
6 Time (min)
8
10
12
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0
Fig. 6 Kinetic study for establishing the rate constants of US assisted interesterification process.
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1/T (1/kelvin) 0 -0.2 -0.4 -0.6 activation energy
-0.8
ln(K)
Linear (activation energy)
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-1 -1.2
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-1.4 -1.6 -1.8
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-2
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Fig. 7 Arrhenius plot for estimation of activation energy.
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80 70
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50 40
ultrasound
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Yield (%)
60
30
conventional
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20 10 0
10
20
30 Time (min)
40
50
60
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0
Fig. 8 Comparison of biodiesel yield in the ultrasound assisted and conventional method with stirring at optimized parameters as 1 wt. % catalyst loading, 60% duty cycle, 1:9 as reactant molar ratio and 50oC temperature.
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80 70
Yield (%)
60 50 40 30
10 0 1
2
3
4 Cycle
5
6
7
8
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0
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20
Fig. 9 Study of γ-alumina reusability in interesterification reaction of karanja oil and methyl
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acetate.
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Table 1. Reaction rate constant and activation energy of reaction for interestrification process.
Rate constant (k)
(oC)
(L/mol min)
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Temperature
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Activation energy
R2
(kJ/mol)
0.16
0.9442
0.29
0.9774
0.36
0.9457
32.68
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50
PT
30
Correlation factor
22
S0255-2701(18)31223-6 https://doi.org/10.1016/j.cep.2018.12.006 CEP 7444
To appear in:
Chemical Engineering and Processing
Received date: Revised date: Accepted date:
8 October 2018 26 November 2018 13 December 2018
Please cite this article as: Kashyap SS, Gogate PR, Joshi SM, Ultrasound assisted intensified production of biodiesel from sustainable source as karanja oil using interesterification based on heterogeneous catalyst (␥-alumina), Chemical Engineering and Processing - Process Intensification (2018), https://doi.org/10.1016/j.cep.2018.12.006 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Ultrasound assisted intensified production of biodiesel from sustainable source as karanja oil using interesterification based on heterogeneous catalyst (γ-alumina)
Shubham S. Kashyap, Parag R. Gogate*, Saurabh M. Joshi.
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Department of Chemical Engineering, Institute of Chemical Technology, Matunga,
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Mumbai, India-400019
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*Correspondence should be addressed
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Email: [email protected]
Graphical-abstract
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Intensified Synthesis of Biodiesel using ultrasound assisted approach 80
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70
50
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Yield (%)
60
40
ultrasound
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conventional
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20 10 0
0
10
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30 Time (min)
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50
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Highlights
First depiction of application of heterogeneous catalyst for intensified interesterification of karanja oil Understanding the effect of operating parameters for maximizing yields
Comparison of ultrasound assisted approach with the conventional stirring
Optimized conditions give about 40% higher product yield for ultrasound
Successful demonstration of the reusability of the catalyst
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Abstract
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Intensification of ultrasound (US) assisted interesterification of karanja oil in the presence of
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γ-alumina as a heterogeneous catalyst was performed in current study. Effect of reaction
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conditions as reactant molar ratio, catalyst loading, duty cycle and temperature on the yield of
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FAME has been investigated. The catalyst used in the work, γ- alumina, is an acidic catalyst and hence is resilient to high FFA and water content, making it as an efficient catalyst as no
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pretreatment is required even for karanja oil as sustainable feed stock. Optimum conditions established in the work for interesterification are 1 wt. % catalyst loading, duty cycle of 60
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%, reactant molar ratio of 1:9 and temperature of 50oC resulting in FAME yield of 69.3% in 50 min. Reusability studies also confirmed that γ-alumina can be reused for six cycles
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without much loss of activity. It was also demonstrated that conventional stirring based approach gave only 50.8% which is much lower than that obtained in the presence of ultrasound. The present study clearly demonstrated that use of ultrasound gives process intensification benefits and there are no negative effects on the γ-alumina used as catalyst as demonstrated by the reuse for six cycles.
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Keywords: Ultrasound; interesterification; γ- alumina; biodiesel; process intensification; sustainable feedstock
1. Introduction
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Throughout human history, use of different fuels with consistent improvisation in the nature
mostly with an objective of enhanced efficiency and lower emissions has always been the
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practice. Earlier in the agrarian era, wood was burned for warmth and cooking and with the invention of steam engines, agrarian economy turned into industrial economy. Steam engines
could be fuelled by both wood and coal. Coal was quickly accepted as a preferred fuel as it
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produced four times energy as produced by same amount of wood. In 20th century,
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technological advancements changed the focus from coal to oil. Refined oil products (petrol
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and diesel) have been in use to power various industries and automobiles, but these are nonrenewable energy resources and also many a times considered to be enhancing the
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atmospheric pollution. Limited availability also makes them scarce and it is essential to seek for some alternative resources. Biodiesel is one of the commercially accepted alternatives for
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non-renewable energy resources available today [1]. Biodiesel can be produced from vegetable oil, animal fat or waste oil mostly based on conversion to alkyl esters [2]. It is
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commonly produced by transesterification of triglycerides and methanol with glycerol as byproduct and requires subsequent separation and purification [3,4]. Though the method is
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commonly used, higher costs of production and generation of the low value product as glycerol has been the major concerns for production. An alternative is the process of interesterification in which alkyl acetate is used instead of alcohol as acyl acceptor group and triacetin is obtained as a byproduct instead of glycerol. Triacetin has more value as compared to glycerol as it is used as solvent and plasticizer and can also be left in product mixture as
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fuel component. Up to 10 wt. % triacetin in biodiesel is allowed as per the ASTM D6451 and EN 14214. Considering these advantages, the present work has focused on interesterification of karanja oil (as a sustainable feed stock). The synthesis processes of interesterification can be catalyzed by acidic, basic or enzymatic catalyst. Basic catalysts are not corrosive in nature but high free fatty acid (FFA) and water
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concentration leads to saponification reaction and hence the problems in processing. Acidic
catalysts are susceptible to water content and usually give lower rates of processing. Mostly
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homogeneous basic catalysts have been used in interesterification reaction using oil with low
FFA content as per the reports in the literature or a two stage esterification followed by
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interesterification has been applied. Homogenous catalysts are soluble in the reaction mixture
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and hence their separation is difficult unlike heterogeneous catalysts which can be recovered
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and reused easily. In the production of biodiesel, final cost is affected mainly by the cost of
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raw material and catalyst. Raw material cost can be reduced using sustainable feed stock (lower costs and no conflict with the main value chain) such as the different non-edible oils
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instead of the edible oils. Catalyst cost can be reduced by using heterogeneous catalyst because it can be effectively reused after easy separation and also the product purification
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step is easier so that the overall production cost reduces. Reusability is an important characteristic of heterogeneous catalysts which reduces the total cost for multiple batches.
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An analysis of the literature revealed that use of heterogeneous catalysts has mostly been only reported for the transesterification of oils. Saha and Goud [5] investigated the
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transesterification of karanja oil using heterogeneous base (Ba(OH)2·8H2O) catalyst in the presence of ultrasound and effect of concentration of catalyst, reaction time, temperature, and reactant molar ratio on the yield of biodiesel was studied. It was reported that maximum of 84% conversion is obtained under optimized operating conditions. Kim et al. [6] prepared Na/NaOH/γ-Al2O3
heterogeneous
base catalyst
and investigated
its
use in the
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transesterification of soy bean oil to biodiesel demonstrating a yield of 94% under optimum conditions. Ribeiro et al. [7] investigated the use of niobium phosphate, γ-alumina, zeolite HY and niobium oxide as the solid catalyst for the interesterification of macaw oil. It was reported that that among all the catalysts used, γ-alumina and niobium phosphate were reported to be most suitable with γ-alumina resulting in FAME yield of 52.5 % in 1 h and
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niobium phosphate requiring 2.5 h for 52.9 wt% as the yield of FAME. Gaikwad and Gogate
[8] synthesized a carbon based heterogeneous catalyst and investigated its application for
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biodiesel synthesis in the presence of ultrasound reporting a maximum of 77.4% of conversion at optimum conditions of 6:1 as the reactant molar ratio, 3 % by weight as the
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loading of catalyst, reaction time as 3 h, temperature as 333 K, ultrasonic power dissipation
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of 120 W and frequency of 20 kHz. Analysis of the literature revealed that there has been no
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report for the intensification of interesterification reaction catalyzed by heterogeneous
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catalysts and hence the present work deals with intensification of interesterification of karanja oil using ultrasound. The selection of karanja oil is justified based on the fact that earlier
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studies have used other sustainable feed stocks for biodiesel production as macaw oil [9] or waste cooking oil [10]. Srivastava and Verma [11] reported the synthesis of biodiesel from
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karanja oil but it was based on the transesterification reaction and intensification studies have not been reported. In summary the current work focuses on the use of karanja oil as a feed
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stock with γ-alumina as heterogeneous acidic catalyst. Ultrasound (US) as process intensification technique was also used in the work with comparison with the conventional
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stirring based approach. Cavities produced by ultrasound grow rapidly and implode on reaching a desired size with generation of micro jets and these micro jets further result in turbulence in the reaction mixture facilitating mass transfer with higher rates of reaction [12]. The current study also aimed at understanding the effects of operating parameters like
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catalyst loading, molar ratio (methyl acetate to oil), US duty cycle and temperature so as to maximize the effects of intensification.
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2. Materials and Method 2.1 Materials
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Karanja oil was procured from Svas Enterprise Pvt. Ltd, Mumbai with the detailed
composition mentioned in our earlier study [13]. Methyl acetate was obtained from S.D. Fine Chem. Ltd., Mumbai whereas acetone and acetonitrile (HPLC grade) were procured from Hi
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Media, Mumbai. γ- alumina, used as catalyst and methyl oleate and methyl linoleate
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standards used in HPLC analysis process were obtained from Sigma-Aldrich.
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2.2 Experimental setup
In the current study, US horn (Dakshin Pvt. Ltd.) was used as source used for ultrasonic (US)
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irradiation with 20 kHz frequency and 120 W power suitable for laboratory scale studies. US horn had a tip diameter of 11mm and was immersed in reaction mixture up to 20 mm. A
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round bottom glass reactor (diameter – 11 mm, capacity – 150 mL) equipped with 3 openings
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(used for sample withdrawal, temperature measurements, agitators or condensers as required) was used for reactions. Water bath was used to control reaction temperature with partial reactor immersion and stirring with help of magnetic stirrer. The overall reaction setup was
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similar as that described in our earlier study on interesterification using homogenous catalyst [13]. Condensation of evaporated methyl acetate vapors was controlled with a reflux condenser attached to vessel. Similar setup without US was used for the conventional approach in the presence of stirring. 2.3 Experimental Methodology 6
The interesterification reaction of karanja oil with methyl acetate was performed in the batch mode at reaction volume of 100 mL. The mixture containing the reactants in desired ratio was heated to the desired temperature and then catalyst was added to the reactor on achieving the required temperature and this point is considered as the start of the reaction. Effect of different operating parameters as catalyst loading (different values as 0.5, 1, 2 and 3% wt),
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duty cycle of ultrasonic horn (different values as 40, 50, 60 and 70%), oil to methyl acetate
molar ratio (OMAMR) (different values as 1:4, 1:9, 1:12 and 1:14) and temperature (different
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values as 30, 40 and 50 °C) on the yield of biodiesel from waste cooking oil has been investigated in the current work. Under the optimized set of operating parameters
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experiments were also performed using conventional approach without US to study degree of
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intensification obtained with US. Progress of the reaction was monitored with periodic
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withdrawal of samples at regular intervals. The withdrawn samples were first washed with hot water. Subsequently, the possible traces of water and methyl acetate were removed by
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heating the samples in crucibles at 150oC. The processed samples were subjected to the
2.4 Analytical method:
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HPLC analysis to estimate the yield of biodiesel.
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Analysis of FAME obtained after interesterification of karanja oil was performed using
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HPLC (Thermo Scientific Acclaim 120) equipped with a UV/visible detector operated at 205 nm and C-18 HPLC column (dimensions: 4.6 × 150 mm). Mobile phase (flow rate of 0.8 mL/min) used for analysis was a solution of acetonitrile and acetone in (70:30 v/v ratios) and
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it was used along with oil sample dissolved (10μL oil in 10mL solution) in the mobile phase for analysis. Amount of the FAME obtained was estimated on comparison of obtained peak areas of the standards (methyl oleate and methyl linoleate). Yield of biodiesel was calculated with the help of following equation:
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Yield of Biodiesel =
Total weight of methyl esters Total weight of oil used
….
(1)
HPLC chromatogram obtained in the current work is shown in Fig.1. Presence of methyl linoleate and methyl oleate in the obtained sample can be confirmed based on the comparison of the peaks obtained at retention time of 8.5 min and 11.19 min respectively with the
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standard [13].
3. Results and discussion 3.1 Effect of catalyst loading on FAME yield
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Effect of catalyst loading on the yield of FAME has been investigated over the range of 0.5
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wt. % to 3 wt. %, keeping values of duty cycle (60%), reactant molar ratio (1:9) and
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temperature (50oC) as constant. Fig 2. depicts the obtained trends for the yield with changes
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in the catalyst loading and it can also be observed from the figure that yield increases from
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60.4% to 69.2% with an increase in catalyst loading from 0.5 wt. % to 1 wt. %. On increasing catalyst loading from 1 wt. % to 2 wt. %, increase in yield was marginal from 69.2% to 72%
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and on further increase in catalyst loading from 2 wt. % to 3wt. %, the yield decreased from 72% to 66.4%. The available number of active sites typically increases with an increase in
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catalyst loading, which results in higher yield initially till the optimum. A subsequent increase in amount of heterogeneous catalyst above optimum makes the reaction mixture too
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dense/viscous resulting in an incomplete dispersion. Increased viscosity is responsible for poor mixing and similar trend was also reported by Kim et al. [6] and hence a decrease in yield on increasing catalyst loading from 2 wt. % to 3 wt. % was observed in the present work. In the current study, an optimum value of catalyst loading of 1 wt. % has been established, while in literature for similar studies, higher loadings of catalysts is reported. Ribeiro et al. [7]
reported an optimum catalyst loading of 5 wt. % in the case of 8
interesterification of macaw oil with conventional stirring method using γ-alumina. Tian et al. [14] reported an optimum catalyst loading of 7.5% in the case of interesterification of triolein as model feedstock using ferric sulfate as heterogeneous catalyst while Gaikwad and Gogate [8] have reported an optimum catalyst loading of 3 wt.% in the case of ultrasound assisted esterification of PFAD using sulfonated carbon catalyst. The comparison with the literature
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has enabled to understand that the optimum catalyst loading is typically specific to the system
and need to be established as per the method reported in the work. It is very important to
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understand that lower optimum as established in the current work mean higher activity of the catalyst.
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3.2 Effect of duty cycle on FAME yield
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Different values of duty cycle ranging from 40% to 70% were used in the work to study the
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effect of duty cycle on FAME yield with values of catalyst loading (1 wt. %), reactant molar
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ratio (1:9) and temperature (50oC) being maintained as constant. Duty cycle decides time for
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which the US source is kept ON and OFF during reaction which further helps to achieve sufficient cooling of ultrasonic horn and also reduce the net power consumption. The results
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obtained for variation in yield with duty cycle depicted in Fig.3 confirm that yield increases from 54.3% to 69.3% with an increase in duty cycle from 40% to 60% which can be
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attributed to the fact that increasing duty cycle increases the cavitation activity which is responsible for increase in yield. A further increase in duty cycle from 60% to 70%, however,
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resulted in a decrease in the yield from 69.3% to 66.4%. Decrease in yield can be attributed to the fact that beyond an optimum value of duty cycle, excess of cavitation causes cushioning effect and lowers the cavitational intensity [15,16] Maddikeri et al. [16] reported similar trend for interesterification of waste cooking oil with 60% as the established optimum duty cycle. Joshi et al. [15] reported an optimum duty cycle of 70% for the transesterification of
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karanja oil whereas Subhedar and Gogate [17] reported an optimum duty cycle of 60% for the enzymatic interesterification of waste cooking oil. 3.3 Effect of reactant molar ratio on FAME yield Effect of reactant molar ratio on the yield of FAME was studied by changing the reactant
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molar ratio from 1:4 to 1:14 keeping the values of catalyst loading constant as 1 wt. %, duty cycle as 60%, and temperature as 50 oC as constant. The obtained trends for the change in
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yield with reactant molar ratio presented in Fig. 4 establish that FAME yield increases from 36.5% to 69.3% with an increase in reactant molar ratio from 1:4 to 1:9 which can be attributed to the fact that increase in concentration of reactants increases the rate of forward
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reaction as interesterification is a reversible reaction [17]. Yield was observed to decrease
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further with an increase in reactant molar ratio beyond the optimum and at 1:14 molar ratio,
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yield was only 58.7%. Similar study on interesterification reported optimum reactant molar
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ratio of 1:12 with 90 % biodiesel yield [16], while Subhedar and Gogate [17] reported an
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optimum reactant molar ratio of 1:9 in the case of ultrasound assisted interesterification of waste cooking oil using immobilized lipase as catalyst. In the case of interesterification of
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triolein using ferric sulfate as heterogeneous catalyst by conventional stirring method, similar trend has been reported but with a requirement of higher reactant molar ratio as 1:20 [14]. In
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another study by Casas et al. [18], 1:48 molar ratio was reported as the best condition in the case of interesterification of sunflower oil using potassium methoxide. Hence it can be said
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that optimum requirement of methyl acetate depends on the specific system in question and hence, importance of current work is established. 3.4 Effect of temperature on FAME yield Experiments were conducted to study the effect of temperature variation on yield of FAME with variation in the temperature from 30oC to 50oC keeping constant values of catalyst 10
loading as 1 wt. %, duty cycle as 60% and reactant molar ratio as 1:9. The obtained data for the yield at various temperatures Fig.5 confirmed that with an increase in temperature from 30oC to 40oC, the yield increased from 48.5% to 62.9% which can be attributed to the fact that higher temperature helps in overcoming the energy barrier with supply of required amount of energy. Miscibility of methyl acetate and oil also increases helping the reaction to
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proceed at faster rate. On further increase in temperature from 40oC to 50oC, increase in the yield was only from 62.9% to 69.3% possibly due to reduction in extent of cavitation activity.
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Higher temperature significantly reduce viscosity and surface tension of liquid which is responsible for reduction in cohesive forces within the liquid and energy required to tear
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apart, thus making cavitation much easier. High temperature also increases the presence of liquid vapors which further produces vaporous cavities leading to cushioning effect during
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compression cycle affecting activity of cavitation. Temperature of 50 oC was considered to be
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the best operating temperature in current study as there was still an increase in the yield (by about 7%) and higher temperatures were not tried in the work due to the boiling point of one
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of the reactants as well as problems with lower cavitational efficiency. Maddikeri et al. [16] also reported similar results for the interesterification of waste cooking oil with optimum
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temperature of 50oC.
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3.5 Kinetic analysis:
Integral analysis was also performed for second order fitting using conversion vs. time data. Fig. 6 shows the data fitting for the second order kinetics at different temperatures of 30oC,
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40oC and 50oC. The reaction kinetics was found to fit well in second order mechanism similar to the literature reports by Maddikeri et al. [16] and Casas et al. [18] in the case of waste cooking oil and sunflower oil respectively. Values of rate constants along with correlation coefficient (R2) are presented in Table 1. Rate constants are found to increase from 0.16 to 0.36 L/mol with an increase in temperature from 30 to 50 oC. Similar trend was reported by 11
Maddikeri et al. [16] in the case of interesterification of waste cooking oil in the presence of ultrasound with an increase in the rate constant from 0.22 to 0.93 (L/mol min) for an increase in temperature from 30oC to 50oC. Activation energy was obtained from plotting data of rate constant and temperature (Fig.7)
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and was calculated to be 32.68 kJ/mol. The work of Maddikeri et al. [16] reported higher activation energy as 58.17 kJ/mol. The comparison establishes the ease of reaction for the
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karanja oil under the processing conditions used in the current work. 4. Comparison of acoustic cavitation with conventional stirring
For conventional process with stirring, optimized parameters (catalyst loading of 1 wt. %,
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reactant molar ratio of 1:9 and temperature of 50 oC) were employed. Comparison of yield
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obtained by ultrasound assisted approach and conventional method under reported optimized
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conditions is presented in Fig. 8. It can be observed from the figure that biodiesel yield
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increased by almost 40 % for ultrasonic assisted technique (actual value of 69.3%) on
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comparison with conventional method (actual value of 50.8%). Literature available on reactions performed conventionally with mechanical stirring also show that such reactions
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don’t give high yield and take more time in comparison to those assisted with ultrasound. Ribeiro et al. [7] reported yield of 52.49% in 1 h for interesterification of macaw oil using γ-
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alumina with conventional stirring method while Tian et al. [14] reported a yield of 75% in 12 hours in the case of interesterification of triolein using ferric sulfate. Study of enzymatic
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interesterification of crambe oil assisted by ultrasound [19] revealed that 38.7 % yield is obtained in 2 h of reaction with US and less than 10% is obtained even after 10h of reaction for conventional process. The reported results suggest that ultrasound accelerates the reaction rate and also reduces the requirement of enzyme compared to reaction without ultrasound. Major problem with conventional stirring method for interesterification reactions is improper mixing because oil is immiscible with methyl acetate. Ultrasound causes cavitation which 12
produces micro jets, local turbulence and micro emulsions which overcomes the problem of mixing and enhances the available interfacial area for the reaction.
5. Reusability of catalyst Reusability is one of the most important characteristic of heterogeneous catalyst as its
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separation from the reaction mixture is easier as compared to homogeneous catalyst. In first run, fresh catalyst was used which was recovered and reused in seven consecutive runs to
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evaluate reusability of γ-alumina. The obtained results shown in Fig.9 established that after
the second cycle, FAME yield decreases marginally from 69.25% to 69% which is not
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significant. In the sixth cycle, the yield decreased to 63.71% whereas in seventh cycle, yield
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was found to be 60%. The reduction in yield can be attributed to the loss of catalyst in the recovery process and reduction in its activity after every run. Ribeiro et al. [7] reported
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reusability of five times for γ-alumina in the case of interesterification of macaw oil with conventional stirring method with 9.1% reduction in yield. In the current study, it was
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observed that with assistance of ultrasound made γ-alumina to be used for six times with only 7.9% reduction in yield. Comparing to conventional stirring method, γ-alumina with
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assistance of ultrasound performed better in terms of reusability attributed to the fact that ultrasound generates microscale cavities which collide and collapse on catalyst surface and
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thus clean the catalyst surface mechanically and help in regeneration. Hence it can be said
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that use of ultrasound increases the reusability of heterogeneous catalyst.
6. Conclusions In the current study, ultrasonic irradiation was demonstrated to be an efficient method for interesterification of karanja oil using heterogeneous catalyst. Ultrasound assistance resulted in significant increase in yield from 50% to 70% as compared to conventional stirring based
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method. The optimum parameters obtained were 1 wt. % as catalyst loading, 60% as duty cycle, 1:9 as reactant molar ratio and 50oC as temperature. Microscale cavities generated by ultrasound collide and collapse on catalyst surface with increased regeneration of catalyst and higher reusability of catalyst. In the current study γ- alumina was successfully reused for 6 cycles with no significant loss of activity. Overall, the most importance finding of the study is
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that heterogeneous catalyst, γ-alumina, resulted in almost 70 % FAME yield from karanja oil
with no requirement of esterification process and easy separation from reaction mixture with
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subsequent reuse.
A.E. Atabani, A.S. Silitonga, I.A. Badruddin, T.M.I. Mahlia, H.H. Masjuki, S.
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[1]
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[13] S.S. Kashyap, P.R. Gogate, S.M. Joshi, Ultrasound assisted synthesis of biodiesel from karanja oil by interesterification: Intensification studies and optimization using RSM,
A
Ultrason. Sonochem.50 (2019) 36-45.
[14] Y. Tian, J. Xiang, C.C. Verni, L. Soh, Biomass and Bioenergy Fatty acid methyl ester production via ferric sulfate catalyzed interesterification, Biomass and Bioenergy. 115 (2018) 82–87. [15] S.M. Joshi, P.R. Gogate, S.S. Kumar, Intensification of ultrasound assisted
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esterification of karanja oil for production of biodiesel with optimization using response surface methodology, Chem. Eng. Process. Process Intensif. 124 (2018) 186– 198. [16] G.L. Maddikeri, A.B. Pandit, P.R. Gogate, Ultrasound assisted interesterification of waste cooking oil and methyl acetate for biodiesel and triacetin production, Fuel
IP T
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SC R
using enzymatic interesterification, Ultrason. Sonochem. 29 (2016) 67–75.
[18] A. Casas, M.J. Ramos, Á. Pérez, Kinetics of chemical interesterification of sunflower
U
oil with methyl acetate for biodiesel and triacetin production, Chem. Eng. J. 171
N
(2011) 1324–1332.
A
[19] G. R. Tavares, J.E. Goncalves, W.D. Santos, C. Silva, Enzymatic interesterification of
A
CC E
PT
ED
M
crambe oil assisted by ultrasound, Ind. Crops. Prod. 97 (2017) 218–223.
16
Figure Caption
Fig. 1 HPLC Chromatogram of biodiesel sample. Fig. 2 Effect of catalyst loading on the yield of biodiesel at constant duty cycle of 60%,
IP T
reactant molar ratio of 1:9 and temperature 50oC.
reactant molar ratio as 1:9 and temperature 50oC.
SC R
Fig. 3 Effect of duty cycle on the yield of biodiesel at constant catalyst loading of 1 Wt. %
Fig. 4 Effect of reactant molar ratio on the yield of biodiesel at constant catalyst loading of 1
U
Wt. %, duty cycle of 60% and temperature at 50oC.
N
Fig. 5 Effect of temperature on the yield of biodiesel at catalyst loading of 1 Wt. %, duty
A
cycle as 60% and reactant molar ratio of 1:9.
M
Fig. 6 Kinetic study for establishing the rate constants of US assisted interesterification
ED
process.
Fig. 7 Arrhenius plot for estimation of activation energy.
PT
Fig. 8 Comparison of biodiesel yield in the ultrasound assisted and conventional method with stirring at optimized parameters as 1 wt. % catalyst loading, 60% duty cycle, 1:9 as reactant
CC E
molar ratio and 50oC temperature. Fig. 9 Study of γ-alumina reusability in interesterification reaction of karanja oil and methyl
A
acetate.
17
IP T SC R U N A M
Fig. 1 HPLC Chromatogram of biodiesel sample.
ED
80 70
PT
0.5 Wt%
30
2 Wt%
50 40
1 Wt%
CC E
Yield (%)
60
3 Wt%
20
A
10 0
0
10
20
30 Time (min)
40
50
60
Fig. 2 Effect of catalyst loading on the yield of biodiesel at constant duty cycle of 60%, reactant molar ratio of 1:9 and temperature 50oC.
18
80 70
50 40%
40
50%
30
60%
20
70%
10 0 10
20
30 Time (min)
40
50
60
SC R
0
IP T
Yield %
60
N
reactant molar ratio as 1:9 and temperature 50oC.
80
A
70
M
60 50 40
1:4 1:9
ED
Yield (%)
U
Fig. 3 Effect of duty cycle on the yield of biodiesel at constant catalyst loading of 1 Wt. %
30 20
PT
10
1:12 1:14
0
CC E
0
10
20
30 Time (min)
40
50
60
A
Fig. 4 Effect of reactant molar ratio on the yield of biodiesel at constant catalyst loading of 1 Wt. %, duty cycle of 60% and temperature at 50oC.
19
80 70
50 40
30C
30
40C 50C
20 10 0 2
4
6 Time (min)
8
10
12
SC R
0
IP T
Yield (%)
60
Fig. 5 Effect of temperature on the yield of biodiesel at catalyst loading of 1 Wt. %, reactant
N A
2.5
M
2
ED
1.5
1
30C 40C 50C
PT
X/(1-X)
U
duty cycle as 60% and molar ratio of 1:9.
CC E
0.5
0
2
4
6 Time (min)
8
10
12
A
0
Fig. 6 Kinetic study for establishing the rate constants of US assisted interesterification process.
20
1/T (1/kelvin) 0 -0.2 -0.4 -0.6 activation energy
-0.8
ln(K)
Linear (activation energy)
IP T
-1 -1.2
SC R
-1.4 -1.6 -1.8
U
-2
A
N
Fig. 7 Arrhenius plot for estimation of activation energy.
M
80 70
ED
50 40
ultrasound
PT
Yield (%)
60
30
conventional
CC E
20 10 0
10
20
30 Time (min)
40
50
60
A
0
Fig. 8 Comparison of biodiesel yield in the ultrasound assisted and conventional method with stirring at optimized parameters as 1 wt. % catalyst loading, 60% duty cycle, 1:9 as reactant molar ratio and 50oC temperature.
21
80 70
Yield (%)
60 50 40 30
10 0 1
2
3
4 Cycle
5
6
7
8
SC R
0
IP T
20
Fig. 9 Study of γ-alumina reusability in interesterification reaction of karanja oil and methyl
A
N
U
acetate.
M
Table 1. Reaction rate constant and activation energy of reaction for interestrification process.
Rate constant (k)
(oC)
(L/mol min)
ED
Temperature
40
Activation energy
R2
(kJ/mol)
0.16
0.9442
0.29
0.9774
0.36
0.9457
32.68
A
CC E
50
PT
30
Correlation factor
22