Exoskeleton of a Mollusk ( Pila globosa ) As a Heterogeneous Catalyst...

Published: November 27, 2011

r 2011 American Chemical Society 11875 dx.doi.org/10.1021/ie202404r | Ind. Eng. Chem. Res. 2012, 51, 11875–11880

ARTICLE

pubs.acs.org/IECR

Exoskeleton of a Mollusk (Pila globosa) As a Heterogeneous Catalystfor Synthesis of Biodiesel Using Used Frying OilShweta Agrawal, Bhaskar Singh, and Yogesh Chandra Sharma*

Department of Applied Chemistry, Institute of Technology Banaras Hindu University, Varanasi 221 005, India

ABSTRACT: A heterogeneous catalyst has been derived from a waste material (i.e., exoskeleton of mollusk) for transesterificationof a waste feedstock (i.e., used frying oil (UFO)) for synthesis of biodiesel. The exoskeleton of mollusk shell was crushed, ground,and calcined at 900 �C to derive CaO as a heterogeneous catalyst. The catalyst was characterized by X-ray diffraction (XRD), Fouriertransform infrared (FTIR) spectroscopy, X-ray fluorescence spectroscopy (XRF), and differential thermal analysis/thermogravi-metric (DT/TG) analysis. The XRD peaks observed at 2θ = 31.80, 36.93, and 53.37� were characteristic of CaO and showed highcrystallinity. The FTIR absorption bands of the calcined shell were observed at 1474, 870, and 502 cm�1, which are attributed to thevibration of CO3

2�molecules, and a sharp peak at 3640 cm�1 indicated the presence of OH� stretching due to Ca(OH)2. The XRFanalysis demonstrated the Pila globosa shell to comprise 79.86% of calcium along with few minor elements (viz. Pd, I, Te, Sb, Sn, W,Al, Si, Sr, Cr, S). The (DT/TG) analysis showed the decomposition of calcium carbonate present in Pila globosa at 860 �C. Thewaste-driven substances (exoskeleton of mollusk as catalyst and UFO as feedstock) resulted in a high yield (92%) and conversion(97.8%) of biodiesel that was obtained at a 10:1 (methanol to oil) molar ratio, 4.0 wt % catalyst, at 60( 0.5 �C in 5 h reaction. Theconversion of UFO to biodiesel was determined by 1H FT-NMR.

1. INTRODUCTION

Biodiesel refers to fuel produced from renewable sources thatmeets widely accepted specifications (e.g., ASTM D 6751).1,2

Biodiesel is manufactured from a variety of plant oils (edible andnonedible), waste cooking oils (e.g., yellow grease), or animal fats(e.g., beef tallow).3 The advantages of usage of biodiesel as trans-port fuel are its high energy return, displacement of petroleumfuel, and reduction of greenhouse gas emissions.4 Biodiesel hasthe potential to eliminate as much as 90% of air toxins such asparticulate matter, hydrocarbons, carbon monoxide, and sulfurdioxide.5,6 Biodiesel (fatty acid alkyl esters) is synthesized usingoils or fats with an alcohol in the presence of a catalyst. Auseful byproduct, i.e., glycerol, is also formed. The fatty acid alkylesters is termed as biodiesel and the byproduct (glycerol) isseparated. The catalyst used in the synthesis process of biodieselis either homogeneous, or heterogeneous (including immobi-lized enzymes).7�9 Alkali catalysts are commonly used in syn-thesis of biodiesel due to their faster rate of reaction and lessercorrosiveness to the equipment used in their production.10

However, heterogeneous catalysts have been explored recentlydue to their easy separation from the product and reusability. Thecommonly employed homogeneous catalysts include NaOH,KOH, and CH3ONa. The heterogeneous group of catalystsconstitutes a wide range including CaO, MgO, hydrotalcite,TiO2 grafted on silica, and vanadyl phosphate.11 Sakai et al.7

used KOH as homogeneous catalyst and CaO as hetero-geneous catalyst for comparison of their economical prospectsin production of biodiesel. The biodiesels obtained from both thecatalysts were purified by either hot water (W) or vacuumdistillation (D) and it was observed that CaO with hot waterpurification process resulted in lowest manufacturing cost amongthe two catalysts with the two modes of purification (KOH-W,KOH-D, CaO-W, CaO-D). Sun et al.8 reports that basicityand activity of the catalyst are correlated. The stronger basicity

of the catalyst resulted in higher yield of biodiesel. Xie et al.12

loaded ZnO with lithium by impregnation method to obtain asolid base catalyst for transesterification of soybean oil andobtained a conversion of 96.3% in 3 h, 12:1 methanol to oilmolar ratio at the reflux of methanol. Sotoft et al.9 used enzymesas catalyst for preparation of biodiesel. However, it was observedthat the enzymes contributed a major portion toward the cost ofbiodiesel. Among the feedstock, the cost ranges were 50% forenzymes, 47% for oil, and 3% for methanol. A lower groupalcohol (preferably methanol) is usually preferred for transester-ification due to faster rate of reaction.13 Biodiesel can also besynthesized by using supercritical methanol without using acatalyst, though the process is cost intensive.14,15 The use ofhomogeneous catalyst (NaOH, KOH, and CH3ONa) poses theproblem of its removal from the product.16 As the catalysts arehighly basic, a stoichiometric amount of acid is required forits neutralization. Also, water is required for the washing ofthe crude biodiesel and consequently a subsequent amount ofwastewater is generated. The yield of biodiesel also decreases onrepeated washing and a large amount of dehydrating agent isneeded to remove water from biodiesel. To overcome theseproblems, heterogeneous catalysts have gained popularity as theycould be regenerated, reused, and make the purification of crudebiodiesel simpler.17 Recently, biodiesel has been utilized as analternative fuel for fishing boats in Taiwan and found that20% substitution of mineral diesel with biodiesel will be cost-effective in accordance with emission reduction.18 The feedstock

Special Issue: Alternative Energy Systems

Received: October 19, 2011Accepted: November 27, 2011Revised: November 24, 2011

11876 dx.doi.org/10.1021/ie202404r |Ind. Eng. Chem. Res. 2012, 51, 11875–11880

Industrial & Engineering Chemistry Research ARTICLE

contributes toward the major cost in the production of biodiesel,which amounts to 75�85% of the total production cost.19

Hence, cheaper alternative feedstocks have been explored inrecent times to produce biofuel that could be economically com-petitive with the prevailing petroleum-based fuel.20 The hetero-geneous catalysts that have been employed by researchers includeNa/NaOH/γ-Al2O3, alum, ion-exchange resin, and SnCl2.

21�24

The synthesis of these catalysts involves several steps that takeslonger time and are mostly cost intensive. Hence, utilization of awaste material as a catalyst can be of immense importance insynthesis of biodiesel to reduce the cost of biodiesel production.To utilize the waste materials as catalyst, researchers haverecently derived CaO from various waste materials viz. chickenegg shell, waste mud crab shell, and mollusk.25�27 The feedstockthat can be used for food should be avoided as raw material forpreparation of biodiesel.28 The use of waste cooking oil as feed-stock can reduce the production cost of biodiesel to a significantextent as it is available at a lower price.29 The cost of waste fryingoil amounts to about half the price of virgin oil.30 Waste cookingand frying oil is generated in huge quantities in many countriesand, at times, they may even be procured without any cost.31,32 Awaste material, Pila globosa also called “Apple Snail”, which isused in experimental work at colleges and discarded after experi-mentation, has been used as a raw material for the synthesis of aheterogeneous catalyst. The global availability of Pila globosa isnot known. However, the genus Pila is native to both Africa andAsia.33 The Pila globosa shells and the fresh organisms are used inayurvedic medicines and eaten as well in India, China, and othernations.34 The life cycle of Pila globosa is less than three monthsand they are reproductive throughout the year.33 In India, thesnail shell is used for dissection purpose in zoology laboratories.In the present work, the mollusk shell, i.e., exoskeleton of Pilaglobosa has been used for preparation of a heterogeneous catalystfor transesterification of used frying oil (UFO) to bring down theproduction cost of biodiesel.

2. MATERIALS AND METHODS

2.1. Materials.The UFO was obtained from a local restaurantat Varanasi, India. The virgin oil of UFO was soybean (refined)oil. Themollusk (Pila globosa) shell was procured from a zoologylaboratory of Agrasen PG College, Varanasi, India. Methanol ofAR grade was obtained from Fischer Scientific Mumbai, Indiaand ortho-phosphoric acid (H3PO4) of AR grade was procuredfrom Merck, Mumbai, India.2.2. Characterization of UFO. The UFO was filtered by

Whatman filter paper (no. 42) to remove the suspended particlespresent in the discarded oil. After filtration, the UFOwas dried ina hot air oven for 2 h at 105 �C to remove the moisture. The acidvalue of the oil was determined by titration with KOH as perASTM D 6751 test method. The fatty acid composition of theUFO was obtained by FT-NMR spectrometer using deutratedchloroform (CDCl3) as solvent.

35

2.3. Catalyst Preparation and Characterization.The DTA/TGA of waste shell of Pila globosawas conducted with StructuredText Analyzer (DTA/TGA)model STA 409Metzsch GeratebauGMBH (Germany) under nitrogen flow at pressure of 1.5 barand flow rate of 2 L/h. The rate of increment of temperature was10 �C per minute. Based on the decomposition temperature ofcalcium carbonate (i.e., 860 �C), the crushed Pila globosa shellwas calcined at 900 �C for 2.5 h in a tubular muffle furnace.Calcination was also done at varying temperatures to observe the

effect of calcination on the catalytic activity. The structural andmicrostructural characterization of the dry powder of calcined Pilaglobosa shell (i.e., CaO) was done by X-ray diffraction (RigakuDMAX III B with Cu�Kα radiation). The functional groups presentin the catalystwere obtained fromVarian 1000FTIR instrument. Thepellets of the catalyst were made by taking 1:50 ratio of catalyst toKBr. The FTIR spectra were recorded in the range of 4000�400 cm�1. The calcined catalyst was also characterized by X-rayfluorescence in ARL OPTIM’X X-ray analyzer (Thermo scientific).2.4. Transesterification Process. The transesterification of

UFO was carried out by taking 100 mL of oil and 40 mL ofmethanol (10:1 molar ratio) with 4.0 wt % of catalyst at a con-stant temperature and constant agitation speed. The entirecontent was placed in a 3-necked round-bottom flask fitted witha mechanical stirrer in the middle neck and a thermometer in theside neck. The UFOwas initially heated to 60 �C. A fixed amountof freshly prepared 4 wt % catalyst�methanol solution (withrespect to oil) was added to the oil. It was taken as the startingtime of the reaction. The heating and stirring were terminatedafter 5 h and the reaction was quenched by applying ice on theouter surface of the round-bottom flask. The products of thereaction were allowed to settle overnight producing three distinctphases (i.e., methyl ester on top, glycerol in the middle, andcatalyst at the bottom). After separation of the methyl ester fromthe glycerol and catalyst phase, 1.0 mL of H3PO4 was added toneutralize the product. H3PO4 has been used for neutralizationinstead of HCl, H2SO4, and HNO3 because of the nontoxicnature of H3PO4. Also, H3PO4 is a weaker acid as compared tothe other acids and hence will cause less corrosiveness.2.5. Analysis of Fatty Acid Methyl Esters (Biodiesel) Con-

version and Yield.The conversion of UFO to methyl esters wasanalyzed by using FT-NMR. The area under the signals of meth-ylene and methoxy protons have been used to monitor the yieldof transesterification.35 Knothe and Kenar36 have derived anequation for the determination of biodiesel (eq 1). The disap-pearance of signal at 4.3 δ and appearance of a sharp peak at3.663 δ indicates the formation of FAME.

C ¼ 100� 2AME

3ACH2

� �ð1Þ

C denotes the conversion (%) of triglycerides to fatty acid methylesters; AME is the integration value of the protons of methylesters, and ACH2

is the integration value of the methyleneprotons. The factors 2 and 3 in numerator and denominatorare attributed to the number of protons (2) on methylene andnumber of protons (3) on methyl ester. The yield was calculatedusing eq 2 given by Leung and Guo.16

Product Yield ð%Þ ¼ weight of product=weight of raw oil� 100

ð2ÞThe error calculated in the measurement of yield of biodieselamounted to (1.0%.

3. RESULTS AND DISCUSSION

3.1. Characterization of the UFO. The density of the UFOwas determined and was found to be 0.9118 kg/L. The viscosityof UFO was determined to be 39.52 cSt at 40 �C. The FT-NMRspectra of UFO were determined. Quaterlet peaks that werecharacteristic of the triglycerides were observed at 4.1 and 4.3,respectively. The proportions of oleic (O), linoleic (L), linolenic



(Ln), and saturated acyl groups (S)were evaluatedusing eqs3�6.37

Ln ð%Þ ¼ 100½B=ðA þ BÞ� ð3Þ

L ð%Þ ¼ 100½ðE=DÞ � 2ðB=A þ BÞ� ð4Þ

O ð%Þ ¼ 100½ðC=2DÞ � ðE=DÞ þ ðB=A þ BÞ� ð5Þ

S ð%Þ ¼ 100½1� ðC=2DÞ� ð6ÞThe proportions for the different acyl groups present have beendepicted in Table 1. The UFO comprises mainly linoleic acid(44.0%), followed by oleic acid (29.9%), whereas, linolenic acid hasbeen found to be absent. The molecular weight of the UFO wasdetermined to be 925.49 g/mol as per the equation given byKomers et al.38

3.2. Characterization of the Catalyst. The Pila globosa shellswere cleaned with tap water and then with double distilled water.It is a hard structured shell and was crushed in an agate mortar.DT/TG Analysis. The decomposition temperature of calcium

carbonate present in the Pila globosa shell was determined bydifferential thermal and thermogravimetric (DT/TG) analysis. A23.0 mg sample of uncalcined mollusk shell was taken fordifferential thermal and thermogravimetric analysis. Figure 1adepicts the decomposition temperature of crushed shell of Pilaglobosa. The weight loss observed from TGA occurred from 380to 860 �C. This indicates the decomposition of CaCO3 present inthe shell initiated at 380 �C. The complete decomposition(accounting for weight loss of 40.48%) was observed at860 �C. The conversion obtained upon calcination of Pila globosaat 800 �C was only 11% which indicates that 800 �C is notadequate for formation of CaO phase. At 860 �C, calciumcarbonate completely decomposed to calcium oxide and carbondioxide (Figure 1a).XRD Analysis. The XRD spectra of the calcined catalyst were

obtained with Cu Kα radiation (λ = 0.15406 nm) at 40 kV,30 mA at a scan speed of 1.0�/min and a scan range of 20�80�.The XRD spectra obtained were compared with the JointCommittee on Powder Diffraction Standards (JCPDS) file.The sharp spectra obtained were an indication of high crystal-linity of the catalyst obtained after calcination. (Figure 1b). Thepeaks that are characteristic of CaO were observed at 2θ = 31.80,36.93, and 53.37�. Similar peaks at 32.3, 37.4, 53.9� characteristicof CaO were also observed by Sharma et al.39 when chickeneggshell was calcined to obtain heterogeneous catalyst. Theoccurrence of minor peaks at 2θ = 63.5 and 67.5 show presenceof some other compounds present in the calcined Pila globosashell in minor amount. Sharma et al.39 observed peaks ofCa(OH)2 at 2θ = 14.7, and 17.8 upon calcination of eggshell.However, no peaks of Ca(OH)2 was observed in the calcined Pilaglobosa shell which may be due to the fact that the diffractionpattern was taken from 2θ = 20� onward.

Table 1. Composition of Fatty Acid Acyl Group

fatty acid acyl groups UFO (%)

linolenic acid (C 18:3) 0

linoleic acid (C 18:2) 44.0

oleic acid (C 18:1) 29.9

saturated fatty acid 25.0

free fatty acid 0.84

total 99.74

Figure 1. Catalyst characterization: (a) DTA/TGA of uncalcinedmollusk shell; (b) XRD of the calcined catalyst at 900 �C; (c) FTIRof the calcined catalyst at 900 �C.



FTIR. The FTIR spectra of Pila globosa shell obtained aftercalcination at 900 �C is depicted in Figure 1c. The spectrum wastaken at room temperature. The absorption bands of the calcinedshell occurred at 1474, 870, and 502 cm�1 which can beattributed to the vibration of CO3

2� molecules. Whereas vibra-tion at 1474 cm�1 occurred due to asymmetric stretch, vibrationsat 870 and 502 cm�1 occurred due to out-of plane bend and in-plane bend for CO3

2� molecules, respectively. A sharp peak at3640 cm�1 indicates the presence of OH� stretching band whichindicates presence of Ca(OH)2 which must have formed fromexposure of CaO to atmospheric air. Similar peaks of calcined catalystat 1470, 820, and 3625 cm�1 were obtained by Sharma et al.39

XRF Analysis. The XRF analysis was carried out on calcinedPila globosa shell at 900 �C for 2.5 h to determine its chemicalcomposition. It was found that calcium is the major elementpresent in the Pila globosa shell which comprised 79.86% of thetotal composition. The elements after calcination of catalystinclude calcium in majority (79.86%) followed by palladium(7.09%), iodine (2.26%), tellurium (2.02%), antimony (1.61%),tin (1.33%), tungsten (1.06%), aluminum (0.594%), silicon(0.554%), strontium (0.549), chromium (0.326%), and sulfur(0.041%). The rest of the unidentified elements together com-prised 2.704%). Viriya-empikul et al.,27 however, report calciumto constitute 99.0% of the total constituent of the golden applesnail shell along with silicon (0.4%), sulfur (0.3%), and strontium(0.2%) as minor constituents.3.3. Estimation of the Percentage Conversion of UFO to

Esters by FT-NMR.The conversion of biodiesel from Pila globosashell was obtained to be 97.8% in 5 h. The FT-NMR spectrum ofbiodiesel obtained is depicted in Figure 2. The experiments wasdone using phase transfer catalyst (tetramethyl ammoniumiodide). Because methanol and oil are insoluble in each other,the quaternary ammonium salt is useful in intermixing of thesetwo phases. However, in the present study, the conversionincreased from 97.8 to 98.11% on use of tetramethyl ammoniumiodide and thus its application appears to be insignificant.Therefore, the phase transfer catalyst was not taken in the presentstudy. Also, the phase transfer catalyst will increase the productioncost of biodiesel synthesis. The single factor experiments of the

variables such as catalyst concentration, reaction temperature, meth-anol to oil molar ratio, and agitation intensity were optimized toobtain a high yield and conversion of biodiesel.3.4. Effect of Catalyst Concentration on Yield.The effect of

catalyst obtained from Pila globosa shell on the transesterificationof the UFO was investigated by varying its concentration from0.5 to 5.0 wt % (based on the molecular weight of UFO). Thereaction was carried out at 60 �C for 5 h and 10:1 methanol to oilratio (i.e., 40 mL methanol in 100 mL of oil). When the catalystconcentration was increased from 4.0 to 4.5 wt %, the yield of thebiodiesel product dropped from 97.78% to 96.0% (Figure 3a).The maximum yield is obtained at 4.0 wt % CaO obtained fromthe calcination of the Pila globosa shell. This amount is higherthan the amount of catalyst (calcined egg shell) used by Sharmaet al.39 However, this amount is quite less than that used byNakatani et al.40 where 25 wt % of the catalyst (calcined oystershell as a source of CaO) was found to be optimum.3.5. Effect of Reaction Temperature.The temperature of the

reaction was varied from 40 to 70 �C with catalyst concentrationof 4.0 wt %. The yield of biodiesel gradually increased by increas-ing the temperature from 40 to 60 �C. A high yield of 97.80% wasobtained at 60 �C. Thereafter, a decrease in the yield wasobserved when the temperature was increased to 70 �C. Methanolhas a boiling point quite below this temperature, and its lossmay haveresulted in lowered yield at this temperature. Hence, 60 �C was theoptimum temperature for a conversion and yield of biodiesel(Figure 3b). This value is near that used by Sharma et al.31 where65( 5 �C was found to be optimum for a high yield of biodiesel.3.6. Effect of Methanol to Oil Ratio. The methanol/oil ratio

is also an important factor affecting the yield of biodiesel. Theeffect of the methanol/oil ratio on the yield of biodiesel at atemperature of 60 �C in the presence of 4.0 wt % calcined CaOcatalyst was studied. The amount of themethanol was varied from 20to 50 mL per 100 mL of oil with 4.0 wt % catalyst amount at 60 �C.Themaximum yield was obtained at 40:100 mL ratio of methanol tooil (Figure 3c). Various researchers have adopted methanol to oilmolar ratio for optimization of methanol amount for transesterifica-tion. Viriya-empikul et al.27 observed 12:1 to be optimum for thetransesterification and Sharma et al.39 found 10:1 methanol to oilmolar ratio to be optimum for synthesis of biodiesel.3.7. Effect of Agitation Speed. The vegetable oil is immis-

cible with methanol. Hence, to overcome the mass transferlimitation, oil and methanol are brought in contact via agitation.Common modes of agitation that can be adopted are magnetic andmechanical agitations. In this study, amechanical stirrerwas used.Thestirring rate of mechanical stirrer used in the present study was variedfrom 500 to 1200 rpm. A much lower yield of biodiesel at 500 rpmwas observed, which increased on increase in rate of agitation. Theoptimum yield was found to be at 1100 rpm. Beyond this, no furtherincrease in the yield was observed. A small decrease (almost thesame that was obtained at 1100 rpm) in the yield of biodiesel wasobtained at 1200 rpm and that is insignificant. At an agitationspeed lower than 1100 rpm, sufficient contact could not beestablished, resulting in a much lowered yield (Figure 3d).The catalyst, Pila globosa shell, fits well as a potential source of

heterogeneous catalyst with high activity after calcination at900 �C. A high yield (92%) and conversion (97.8%) of biodieselwere obtained at a moderate methanol to oil molar ratio (i.e.,10:1), 4.0 wt % catalyst at 60 ( 5 �C in 5 h, and is comparablewith the findings of other authors. Sharma et al.40 also obtaineda high yield and conversion of 95.0% and 97.4%, respectively,using chicken eggshell (calcined at 900 �C) as catalyst and

Figure 2. FT NMR spectrum of biodiesel obtained from Pila globosashell catalyst concentration 4 wt %, 8:1molar ratio of methanol to oil, 5 hstirring.



Pongamia pinnata as feedstock at a comparatively lowermethanolto oil molar ratio (i.e., 8:1), catalyst amount (2.5 wt %), and time(2.5 h) at 65( 5 �C.Wei et al.25 calcined the eggshell at 1000 �Cto formCaO as catalyst and obtained 95% yield of biodiesel at 9:1methanol to oil molar ratio, 3 wt % of catalyst at 65 �C in 3 h.Boey et al.26 reported the optimum conditions for transesterifica-tion using Scylla serrata shell as catalyst calcined at 700 �C (toderive CaO) to be methanol to oil mass ratio of 0.5:1, catalystamount of 0.5 wt % at 65 �C, with the agitation rate of 500 rpm toobtain a high conversion (>99%) of biodiesel. Viriya-empikulet al.27 found the catalytic activity of golden apple snail (Pilaglobosa) shell to be comparable with that of eggshell uponcalcination at 800 �C obtaining a high yield (>95%) of biodieselthough a comparatively higher catalyst amount (10 wt %) andmethanol to oil molar ratio (12:1) at 60 �C.

4. CONCLUSIONS

CaO is a very widely used catalyst for biodiesel synthesis, butmost of these catalysts are of commercial grade. The exoskeletonof mollusk (Pila globosa) was calcined at 900 �C for 2.5 h for theconversion of CaCO3 to CaO. The CaO obtained was utilized as

a heterogeneous catalyst for synthesis of biodiesel from UFO.The usage of waste products both as catalyst and feedstock bearseconomic as well as environmental significance. The cost ofbiodiesel synthesis is reduced and a sustainable environment ismaintained. The conversion of feedstock to biodiesel was foundto be 97.8% using 4.0 wt % of catalyst with 10:1 molar ratio ofmethanol to oil. The international European Nation (EN) normwith a minimum value of 96.5% has also been fulfilled.

’AUTHOR INFORMATION

Corresponding Author*E-mail: [email protected]. Tele.: +91 542 6702865. Fax:+91 542 2368428.

’ACKNOWLEDGMENT

S.A. is thankful to UGC for grant of Junior Research Fellowship.

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Figure 3. (a) Effect of catalyst concentration on yield (%) of used frying oil methyl esters. [methanol to oil ratio, 8:1; temperature, 60 �C; agitationspeed, 1100 rpm; reaction time, 5 h]. (b) Effect of temperature on yield (%) of used frying oil methyl ester [methanol to oil ratio, 8:1; catalyst amount,4.0 wt %; agitation speed, 1100 rpm; reaction time, 5 h]. (c) Effect of methanol ratio to oil on yield (%) of used frying oil methyl ester [catalyst amount,4.0 wt %; agitation speed, 1100 rpm; reaction temperature, 60 �C; reaction time, 5 h]. (d) Effect of agitation speed on yield (%) of used frying oil methylester [methanol to oil ratio, 8:1; catalyst amount, 4.0 wt %; reaction temperature, 60 �C; reaction time, 5 h].



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Exoskeleton of a Mollusk ( Pila globosa ) As a Heterogeneous Catalyst...

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