Biodiesel production by esterification of free fatty acid over sulfated zirconia

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Renewable Energy 51 (2013) 227e233

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Renewable Energy

journal homepage: www.elsevier .com/locate/renene

Biodiesel production by esterification of free fatty acid over sulfated zirconia

Anjali Patel*, Varsha Brahmkhatri, Namita SinghDepartment of Chemistry, Faculty of Science, M. S. University of Baroda, Vadodara 390002, India

a r t i c l e i n f o

Article history:Received 13 February 2012Accepted 20 September 2012Available online 24 October 2012

Keywords:Sulfated zirconiaBiodieselOleic acidEsterificationMethanol

* Corresponding author. Tel.: þ91 265 2795552.E-mail address: aupatel_chem@yahoo.com (N. Sin

0960-1481/$ e see front matter � 2012 Elsevier Ltd.http://dx.doi.org/10.1016/j.renene.2012.09.040

a b s t r a c t

Sulfated zirconia was synthesized and characterized by various physico-chemical techniques such as EDS,Thermal analysis (TGA & DTG), FT-IR, XRD, BET surface area measurement, SEM and n-butyl amine aciditydetermination. The use of synthesized catalyst was explored for biodiesel production by esterification of(free fatty acid) oleic acid with methanol. Influence of various reaction parameters (catalyst concentra-tion, acid/alcohol molar ratio, catalyst amount, reaction temperature and reaction time) on catalyticperformance was studied to optimize the conditions for maximum yield of methyl oleate. Also thecatalyst was regenerated and reused. As an application, preliminary study was carried out for biodieselproduction by transesterification of waste cooking oil and Jatropha oil, as feedstock without anypretreatment, with methanol.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

Biodiesel is a renewable, biodegradable and non-toxic fuel.Biodiesel production has become a very intense research area dueto rapidly depleting energy reserves and fluctuating petroleumprices [1]. Fatty acid methyl ester (FAME) commonly known asbiodiesel can be a potential renewable energy fuel which canreplace petroleum-derived diesel [2e5].

The conventional biodiesel production process based on the useof alkaline catalyst, such as sodium hydroxide or sodium meth-oxide, for transesterification of triglyceride posed serious separa-tion problem. The presence of water and/or free fatty acids (FFA) inthe reaction system leads to saponification [3,6,7]. A homogeneousacid catalyst, such as sulfuric acid or hydrochloric acid can also beused [8,9], which does not produce soap and increase the fuelproduction. However, corrosiveness and the down-streamingseparation are the main problems. To avoid these problems,heterogeneous acid catalysts could be used. Also working withheterogeneous acid catalysts improves economic issues and betterprofitability of the biodiesel production process [10].

Among the various available heterogeneous acid catalysts,sulfated zirconia finds enormous applications in biodiesel produc-tion, especially due to its high catalytic activity and selectivitytowards the ester when fatty acid reacts with a large variety ofalcohols [2,8,9,11].

gh).

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Rothenberg and co-workers have reported the use of sulfatedzirconia, titania and stannia esterification reactions of free fattyacids, but the former was still the most active [3]. Jitputti and co-workers have reported that sulfated zirconia can give promisingresults in transesterification of palm kernel oil and crude coconutoil with methyl ester yield reaching as high as 90.3% and 86.3%,respectively [11]. Chen and his group had also evaluated the cata-lytic activity of SO2�

4 =ZrO2 for transesterification of cotton seed oil,rich in free fatty acid content to produce fatty acid methyl esters[12]. Meunier and co-workers have reported a study focused on theesterification of a synthetic mixture of palmitic acid in sunflower oilwith methanol over sulfated zirconia [13]. Lee and co-workers havealso reported the use SO2�

4 =ZrO2 for the esterification of free fattyacids present in used vegetable oils, waste cooking oil (WCO) withmethanol [14]. Xiao and co-workers have used sulfated zirconia ascatalysts for the transesterification of waste cooking oil withmethanol [15].

Sulfated zirconia has also been reported for biodiesel productionby esterification of free fatty acids such as dodecanoic acid with2-ethyl hexanol [16,17] and for palmitic acid with methanol [13].Recently K. T. Lee and co-workers have reported transesterificationof Jatropha curcas oil by SO2�

4 =ZrO2 and studied the effect ofinteraction between process variables [18]. Dussadee Rattanaphraand co-workers have reported esterification of myristic acid withmethanol in presence of triglycerides over sulfated zirconia [19]. Atthe same time there are no reports on the esterification of oleic acidfor biodiesel production using sulfated zirconia as catalyst.

Therefore, it was thought of interest to explore the catalyticactivity of sulfated zirconia for biodiesel production by esterification

Table 1Weight % of SO2�

4 onto ZrO2.

Catalyst Weight % of SO2�4

0.1 N SO2�4 =ZrO2

5.0

0.2 N SO2�4 =ZrO2

26.3

0.3 N SO2�4 =ZrO2

40.0

1.0 N SO2�4 =ZrO2

68.5

Table 2Elemental analysis (EDS).

Materials Elements (Weight %)

O Zr S

Analytical Theoretical

SO2�4 =ZrO2

49.12 47.98 2.90 1

C SO2�4 =ZrO2

39.62 58.96 1.42 1

A. Patel et al. / Renewable Energy 51 (2013) 227e233228

of oleic acid. In the present work, sulfated zirconia was synthesizedand characterized by various physico-chemical techniques such asEDS, Thermal analysis (TGA & DTG), FT-IR, XRD, BET surface areameasurement, SEM and n-butly amine acidity determination. Theeffect of various reaction parameters such as catalyst concentration,acid/alcohol molar ratio, catalyst amount, reaction temperature aswell as reaction time were studied to optimize the conditions formaximum yield for fatty acid methyl ester (FAME). Also the catalystcan be regenerated and reused. As an application, preliminary studywas carried out for biodiesel production by transesterification ofwaste cooking oil and Jatropha oil, as feedstock without anypretreatment, with methanol over the present catalyst.

2. Experimental

2.1. Materials

All chemicals were of A.R. grade. Zirconium oxychloride wasobtained from Loba chemie, Mumbai, and used as received.Methanol, Oleic acid and liquor ammonia were obtained fromMerck and used as received.

2.2. Synthesis of hydrous zirconia

Hydrous zirconia was prepared by adding an aqueous ammoniasolution to an aqueous solution of ZrOCl2$8H2O upto pH 8.5. Theresulted precipitates were aged at 100 �C in a water bath for 1 h,filtered, washed with conductivity water until chloride free waterwas obtained and dried at 100 �C for 10 h. The obtained materialwas designated as ZrO2.

2.3. Synthesis of the catalysts

A series of catalysts were synthesized by the wet impregnationof 1 g of ZrO2 with 15 ml aqueous solution of 0.1, 0.2, 0.3 and 1 Nsulfuric acid for 10 h with occasional stirring. The solutionwas thenfiltered and the obtained materials were dried at 120 �C for 10 h.The resulting materials were designated as 0.1 N SO2�

4 =ZrO2, 0.2 NSO2�

4 =ZrO2, 0.3 N SO2�4 =ZrO2 and 1.0 N SO2�

4 =ZrO2 respectively. Thefiltrates solutions were analyzed for SO2�

4 and the remaining sulfatewas subtracted from the total sulfate, which gives the weight % ofSO2�

4 supported to ZrO2. The selected catalyst i.e. 1 N SO2�4 =ZrO2

was calcined at 600 �C for 4 h. The obtained material was desig-nated as C SO2�

4 =ZrO2.

2.4. Characterization

Elemental analysis was carried out using JSM 5910 LV combinedwith INCA instrument for EDS- SEM. Thermal analysis of the samplewas obtained by using the INKARP Thermal Analysis System (TG/DTA 6300). FT-IR spectra of the samples were obtained using KBrpellet on Perkin-Elmer. The structural information was carried outby the XRD pattern using PHILIPS PW-1830. The conditions usedwere: Cu Ka radiation (1.5417�A), scanning angle from 5� to 60�. Thesurface morphologies of the support and catalyst were studied bySEM using a Jeol SEM instrument (model-JSM 5610 LV) withscanning electrode at 15 kV. AdsorptioneDesorption isotherms ofsamples were recorded on a micromeritics ASAP 2010 surface areaanalyzer at �196 �C. From the AdsorptioneDesorption isothermsspecific surface area was calculated using BET method.

2.5. n-butyl amine acidity determination

The total acidity for all the materials was determined by n-butylamine titration [20]. A 0.025M solution of n-butyl amine in toluene

was used for estimation. The catalyst weighing 0.25 g was sus-pended in this solution for 24 h and excess basewas titrated againsttrichloroacetic acid using neutral red as an indicator. This gives thetotal acidity of the material.

2.6. Catalytic reaction

The esterification of oleic acid with methanol was carried out ina 100ml batch reactor provided with a double walled air condenser,magnetic stirrer and a guard tube. The reaction mixture was dilutedto 100mlwithmethanol up to themark; 5ml of diluted solutionwastaken for the determination of unreacted acid. This was titratedagainst 0.1M standardizedmethanolic NaOH solution. Blank readingwas found out by diluting the definite quantity of oleic acid to 100mlusing methanol. 5 ml of this solution was titrated against 0.1 Mstandardized methanolic NaOH solutions using phenolphthaleinindicator. Difference between the blank reading and reading forreaction mixture was used for finding out the % yield of ester.

3. Results and discussion

As shown in Table 1, 1.0 N SO2�4 =ZrO2, containing maximum

weight % SO2�4 , was selected for detailed study. For convenience, it

was once again coded as SO2�4 =ZrO2. Table 2 shows the elemental

analysis (EDS) for 1 N SO2�4 =ZrO2 and C SO2�

4 =ZrO2. The observedvalues of elemental analysis were in good agreement with theo-retically calculated values.

The TGA and DTG for the SO2�4 =ZrO2 is shown in Fig. 1. TGA

showed that SO2�4 =ZrO2 was thermally stable. There was an initial

weight loss observed from room temperature to 150 �C due toadsorbed water, after that there was negligible weight loss up to350 �C and 550 �C, which indicates that thematerial was stable up to600 �C. It is known that at higher temperature hydrous zirconiaundergoes a phase change and it was clearly observed from DTGcurve. TheDTGcurve showed thephase changeof ZrO2which startedat 400 �C indicating the phase change frommonoclinic to tetragonal.Hence, the sample SO2�

4 =ZrO2 was calcined at 600 �C for 4 h.FT-IR spectra of SO2�

4 =ZrO2 (Fig. 2), shows a broad band at3391 cm�1 corresponding to the OH stretching vibration and alsothe band at 1631 cm�1 corresponding to d HOH [21]. The bands at1235, 1132, 1054 and 987 cm�1 indicated the presence of SO2�

4 , andwere in good agreement with the reported one [22]. FT-IR spectraof C SO2�

4 =ZrO2 (Fig. 2), shows that the calcination, at 600 �Cmodifythe position of SO2�

4 bands and shift towards higher wave number.The SO2�

4 bands were replaced by a very broad band witha shoulder at 1379, 1233 and 1042 cm�1. The OH stretching band at

Fig. 1. TGA and DTG of SO2�4 =ZrO2.

A. Patel et al. / Renewable Energy 51 (2013) 227e233 229

3391 cm�1 decreased rapidly while d HOH band at 1631 cm�1

changed little.XRD patterns of SO2�

4 =ZrO2 and of C SO2�4 =ZrO2 were shown in

Fig. 3. XRD of SO2�4 =ZrO2 showed that the sample was amorphous.

Fig. 2. FT-IR of ZrO2, SO2�4 =ZrO2 and C SO2�

4 =ZrO2.

On calcinations at 600 �C, displayed a well distinguished peaks at2q ¼ 30, assigned to tetragonal phase of ZrO2 [22]. The SO2�

4 =ZrO2sample exhibited poor crystallinity with a mixture of monoclinicand tetragonal phases. On the other hand, the C SO2�

4 =ZrO2 sampleexhibited prominent lines due to tetragonal phase, indicating thatthe impregnated sulfate ions show a strong influence on the phasemodification of zirconia from thermodynamically more stablemonoclinic to the metastable tetragonal phase.

The SEM of ZrO2, SO2�4 =ZrO2 and C SO2�

4 =ZrO2 are shown inFig. 4(a), (b) and (c). The SEM of SO2�

4 =ZrO2 showed that the surfaceof ZrO2 was distinctly altered, exhibiting considerable surfaceshining after sulfation. SEM images taken at higher magnificationclearly showed the alternation and shining of the surface. This maybe due to the presence of highly charged species, i.e. SO2�

4 ions. TheSEM images of C SO2�

4 =ZrO2 were almost same as compared tosulfated zirconia.

For the ZrO2, SO2�4 =ZrO2 and C SO2�

4 =ZrO2 catalysts, surface areameasurement, pore volume and total surface acidity obtained from

Fig. 3. XRD of 1 N SO2�4 =ZrO2 and 1 N C SO2�

4 =ZrO2.

Fig. 4. SEM of (a) ZrO2, (b) SO2�4 =ZrO2 and (c) C SO2�

4 =ZrO2.

Table 3BET surface area, pore volume as well as acidity of ZrO2, SO2�

4 =ZrO2 andC SO2�

4 =ZrO2.

Catalyst Surface area(m2/g)

Pore volumecm3/g

n-butyl amine acidity(mmol/g)

ZrO2 170 e e

SO2�4 =ZrO2

128.8 0.07563 0.93

C SO2�4 =ZrO2

46.03 0.06317 1.43

A. Patel et al. / Renewable Energy 51 (2013) 227e233230

n-butyl amine titration method are shown in Table 3. The surfacearea decreases from ZrO2 to SO2�

4 =ZrO2, as expected. Further it alsodecreases from SO2�

4 =ZrO2 to C SO2�4 =ZrO2, due to calcinations.

Pore volume also decreases for C SO2�4 =ZrO2, as shrinking of the

lattice on calcinations due to loss of water that takes place. The n-butyl amine acidity gives an idea about total acidity of the material.For SO2�

4 =ZrO2, on sulfation, acidity increases which may be due topresence of SO2�

4 ions on the surface of ZrO2, as expected. Acidityfurther increases in C SO2�

4 =ZrO2, which may be due to theformation of tetragonal phase as well as the increase in Lewisacidity of zirconia due to calcinations.

3.1. Esterification of oleic acid with methanol

Esterification is an equilibrium-limited reaction. In order toovercome the equilibrium limitation, generally esterification of free

Scheme 1. Esterification

fatty acids is carried out by taking alcohol in excess in order to favorthe forward reaction. The esterification of free fatty acid withmethanol in presence of catalyst is shown in Scheme 1. The effect ofvarious reaction parameters such as catalyst concentration, acid/alcohol molar ratio, catalyst amount, reaction temperature andreaction time on catalytic performance was studied to optimize theconditions for maximum yield for fatty acid methyl ester (FAME).

To study the effect of % loading of SO2�4 the esterification reac-

tion was carried out with 0.1 N SO2�4 =ZrO2, 0.2 N SO2�

4 =ZrO2 ,0.3 NSO2�

4 =ZrO2 and 1 N SO2�4 =ZrO2 .The obtained results are shown in

Table 4. It was observed that with increase in the % loading of SO4, %yield also increases; this may be due to increase in acidic activesites on the surface on increasing the concentration of acid. Themaximumyield obtained was 18.0% for 1.0 N SO2�

4 =ZrO2 catalyst. Inorder to increase the % yield, the 1.0 N SO2�

4 =ZrO2,ðSO2�4 =ZrO2Þ

catalyst was calcined at 600 �C for 4 h. The obtained material wasdesignated as C SO2�

4 =ZrO2. Hence the detailed studies (such asmolar ratio, amount of catalyst, reaction time and reactiontemperature) were carried out using C SO2�

4 =ZrO2. Each result wastested by repeating the experiment three times and mean of thethree results has been reported. However the uncertainty analysisis incomplete.

In order to see the effect of mole ratio, the reaction was carriedout by varying mole ratio of oleic acid to methanol as shown inFig. 5. The % yield increased with increase in oleic acid/methanolratio and reached maximum 40% at mole ratio of 1:40. With further

of free fatty acids.

Table 4Effect of % loading of SO2�

4 :

Catalysta % Yield

0.1 N SO2�4 =ZrO2

8

0.2 N SO2�4 =ZrO2

8

0.3 N SO2�4 =ZrO2

10

1.0 N SO2�4 =ZrO2

18

a Reaction conditions: mole ratio 1:40; amount ofcatalyst 0.1 g; temperature 60 �C; reaction time 4 h.

0

10

20

30

40

50

60

70

80

4 8 12 14

% Y

ield

Reaction time (h)

Fig. 6. Effect of reaction time, reaction conditions: mole ratio 1:40; catalyst amount0.1 g; temperature 60 �C.

0

10

20

30

40

50

60

70

80

90

100

0.1 0.15 0.2 0.3 0.4 0.5 0.6 0.75

% Y

ield

Catalyst concentration (g)

Fig. 7. Effect of catalyst amount, reaction conditions: mole ratio 1:40; temperature60 �C; reaction time 12 h.

A. Patel et al. / Renewable Energy 51 (2013) 227e233 231

increase in molar ratio there was decrease in % yield of ester.Initially with increase in methanol concentration, ester yieldincreased from 23 % to 40 % when the molar ratio changed from1:20 to 1:40. On further increasing the alcohol concentration,equilibriumwas attained and no further increase in % yield of esterwas observed. This can be explained by competitive adsorption ofreactants on catalyst. Further increasing methanol in the reactionmixture, majority of the sites on the catalyst surface were occupiedby methanol molecules. Hence fewer sites remain available for theoleic acid. Hence molar ratio of 1:40 was optimum for obtaininghigh yield products. Further the results were cross checked bycarrying out GC analysis, (Nucon-5700) using a BP1 capillarycolumn and the results are in the acceptable limit (Fig. 5).

The effect of reaction time on oleic acid was investigated. Asshown in Fig. 6, the % yield increased with increase in reaction timeand reaches maximum 71% after 12 h. But with further increasingthe reaction time, the % yield decreased, as after 12 h of reactiontime, the active sites of the catalyst may get blocked by products.The maximum yield reached 71% in 12 h.

The effect of reaction temperature was also studied; attemperature 60 �C maximum % yield was achieved. Hence, theoptimum temperature for oleic acid esterification is 60 �C. Furtherincreasing the reaction temperature upto 80 �C, % yield of esterdecreases to 58%. Usually the increase in reaction temperature,should lead to usual increase of reaction extent but it could alsocause acceleration of secondary reactions which reduce the yieldtowards desired product [22].

The effect of amount of catalyst on % yield was investigated. Thecatalyst amount was varied in the range of 0.1e0.75 g. As shown inFig. 7, the % yield increased with increase in catalytic amount of 1 NC SO2�

4 =ZrO2 and reaches maximum of 90% conversion. But withfurther increase in amount of catalyst the % yield was constant andthen decreased which may be due to blocking of active sites. Themaximum % yield reaches 90% with 0.5 g of catalyst. Hence it wasselected for the esterification of oleic acid.

The optimized conditions for the esterification of oleic acid withmethanol using C SO2�

4 =ZrO2 is as follows: mole ratio of acid to

0

5

10

15

20

25

30

35

40

45

1:20 1:40 1:60 1:80 1:120

% Y

ield

Mole ratio (acid:alcohol)

Titration method

GC Data

Fig. 5. Effect of mole ratio (acid/alcohol), reaction conditions: catalyst amount 0.1 g;temperature 60 �C; reaction time 4 h.

alcohol 1:40; amount of catalyst 0.5 g; reaction temperature 60 �C;reaction time 12 h was obtained.

The control experiment with ZrO2 was also carried out underoptimized conditions. It can be seen from Table 5, that ZrO2 was notmuch active towards the esterification of oleic acid indicating thecatalytic activity is due to SO2�

4 . Thus, we were successful insynthesizing a heterogeneous sulfated zirconia catalyst and inovercoming the traditional problems of homogeneous catalyst.

3.2. Recycling of the catalyst

The catalyst was recycled in order to test its activity as well asstability. The catalyst was separated from the reaction mixture onlyby simple filtration, first washed with methanol till the filtrate isfree from the acid, i.e. unreacted oleic acid if any, followed bywashings with double distilled water, dried and then calcined at600 �C. The regenerated catalyst was designated as R C SO2�

4 =ZrO2and it was characterized by elemental analysis (EDS), FT-IR, XRDand SEM.

Table 5Control experiment for esterification of oleic acid.

Materiala % Yield

ZrO2 32C SO2�

4 =ZrO2 90

a Reaction conditions: mole ratio 1:40; tempera-ture 60 �C; reaction time 12 h; catalyst amount 0.5 g.

Table 6Elemental analysis (EDS) of recycled catalyst ðR C SO2�

4 =ZrO2Þ.

Catalyst Elements (Weight %)

O Zr S

Analytical Theoretical

C SO2�4 =ZrO2

39.62 58.96 1.42 1.0

R C SO2�4 =ZrO2

37.77 61.23 0.99 1.0

Table 7FT-IR band assignments of fresh and regenerated catalyst.

Material FT-IR band assignments (wave number cm�1)

(n) OeH stretching (d) HeOeH bending SO2�4

C SO2�4 =ZrO2 3391 1631 1379

12331042

R C SO2�4 =ZrO2 3399 1622 1384

12531041

Fig. 8. XRD of fresh ðC SO�24 =ZrO2Þ and recycled ðR C SO�2

4 =ZrO2Þ catalyst.

A. Patel et al. / Renewable Energy 51 (2013) 227e233232

3.3. Characterization of recycled catalyst

EDS analysis for fresh catalyst, C SO2�4 =ZrO2 and the regenerated

catalyst, R C SO2�4 =ZrO2 are shown in Table 6. The observed value of

elemental analysis for recycled catalyst is same as that of the fresh

Fig. 9. (a) SEM of (a) C SO2�4 =Zr

catalyst. This indicates no leaching or loss of SO2�4 from the surface

of ZrO2 during the reaction.Table 7 shows FT-IR band assignments of fresh catalyst

C SO2�4 =ZrO2 and recycled catalyst, R C SO2�

4 =ZrO2. The FT-IRspectra of the R C SO2�

4 =ZrO2 showed band at 3399 cm�1 corre-sponding to the OH stretching vibration and also the band at1622 cm�1 corresponding to d HOH, that has reduced rapidly. TheSO2�

4 bands were obtained as a broad band with a shoulder at 1384,1253, 1135, 1041 cm�1. No appreciable shifting in the FT-IR bandposition of the regenerated catalyst compared to fresh catalyst, i.e.C SO2�

4 =ZrO2 indicates the retention of its structure.The XRD pattern for the fresh catalyst C SO2�

4 =ZrO2, as well asthe regenerated catalyst, R C SO2�

4 =ZrO2 are shown in Fig. 8. Therewas no appreciable change in XRD spectra of fresh as well asregenerated catalyst indicating the stability of the catalyst afterregeneration. The powder XRD of R C R C SO2�

4 =ZrO2 did not showany additional peak indicating that it did not decompose afterregeneration and it retained the tetragonal phase of zirconia.

Fig. 9(a) and (b) shows SEM of fresh catalyst C SO2�4 =ZrO2 and

recovered catalyst, R C SO2�4 =ZrO2. The surface morphology of

R C SO2�4 =ZrO2 was almost same as compared to fresh catalyst. As

well as it retains its considerable surface shining as compared to thefresh catalyst.

3.4. Catalytic activity of recycled catalyst

The recovered catalyst was charged for the further run underoptimized conditions. As seen from Table 8, the recycled catalystdid not show any appreciable change in the activity, indicating thatthe catalyst is stable and can be regenerated for repeated use.

4. Application of the catalyst

As an application, preliminary studies were carried out forbiodiesel production by transesterification of waste cooking oil andJatropha oil, as feedstock without any pretreatment, with methanolover the present catalyst.

4.1. Transesterification reaction

Transesterification of triglycerides (TGs) with low molecularweight alcohols produces biodiesel. The typical reaction of trans-esterification was carried out in a 100 ml batch reactor, providedwith thermometer, mechanical stirring and condenser. Wastecooking oil and methanol were added in 1:40 mole ratio and fol-lowed by catalyst addition, then reaction mixture was held at 65 �Cfor 12 h with stirring at 600 rpm order to keep system uniform in

O2 and (b) R C SO2�4 =ZrO2.

Table 8Esterification of oleic acid with fresh and regeneratedcatalyst.

Catalystsa % Yield

C SO�24 =ZrO2

90

R C SO�24 =ZrO2

87

a Reaction conditions: mole ratio 1:40; temperature60 �C; reaction time 12 h; catalyst amount 0.5 g.

Table 9Transesterification of different feedstocks using C SO2�

4 =ZrO2.

Feedstock Amount of oil taken(g)/amount of alcoholtaken (ml)

Reactiontime (hrs)

Catalystamount (g)

% conversion

WCO 4/16.2 12 0.5 82Jatropha oil 4/16.2 12 0.5 80

A. Patel et al. / Renewable Energy 51 (2013) 227e233 233

temperature and suspension. After the reaction is completed, themixture was rotary evaporated at 50 �C to separate the methylesters. The conversion of FFA in the WCO to biodiesel was calcu-lated bymeans of the acid value (AV) of the oil layer using followingequation. The transesterification of Jatropha oil with methanol wascarried out by following the same procedure.

Conversion ð%Þ ¼�1� AVOL

AVWCO

�� 100

Where, OL and WCO refer to oil layer and waste cooking oilrespectively.

The conversion of FFAs in waste cooking oil (WCO) and Jatrophaoil is shown in Table 9. The present catalyst exhibits excellentactivity in transesterification of triglyceride feedstocks, wastecooking and Jatropha oil without any pretreatment.

5. Conclusion

TGA analysis shows that the catalyst is stable up to 600 �C. Thepresent work shows that C SO2�

4 =ZrO2, exhibits significant activitytowards biodiesel production by esterification of oleic acid undermild conditions, with maximum 90% yield of methyl oleate. Alsothe catalyst shows the potential of being used as a recyclablecatalytic material after a simple regeneration without any signifi-cant loss in activity. Studies also reveal that the catalyst could beused for biodiesel production from waste cooking oil and Jatrophaoil without any pretreatment. Hence the present catalyst can beemployed for the feedstocks that are rich in free fatty acids.

Acknowledgments

One of the authors, Ms. Varsha Brahmkhatri, is thankful toDST INSPIRE fellowship, New Delhi for the financial assistance.

Anjali Patel is thankful to Department of Science and Technology(DST, No. SR/S5/GC-01/2009) for financing a part of this work.

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