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7 t h Biom ass Asia Worksh op, Nove m be r 29-De cem be r 01, 2010 , J akarta, I ndon es ia Ultrasonic on Transesterification Reaction for Biodiesel Production Siriporn La rpkia tta worn 1 * , Cha lerm cha i J e era pa n 1 , Rattikan Tongpan 1 , Si ripo rn Tong on 1   Th a ila n d Ins t it u t e o f Sc ie nt ific an d Te c h no lo g ic a l Re s ea r c h (TIS TR) , Pa t h um Th an i, Th a ila n d 1  Ema il: siripo rn@t istr.or.th Abstract I n th is work, the effect of ultras onic on the tran se ste rification rea ction of jat ropha oil to biodies el was studied i n both homoge neous a nd he terogeneous ca talyst system s.  All rea ctions we re ope rate d a t 9:1 m etha nol t o oi l ratio. I n h om ogen eous cata lyst system , the ultrasoni c powe r of 1500 W a nd f reque ncy of  20 kHz were applied to the mixture of hot oil (100 o C) and methanol with 0.5% NaOH. The ultrasonic transe steri ficati on rea ction ti me of 10, 20, an d 30 se c were varied . I t was found that at the 20 sec reacti on time, biodiesel can be produced with high m ethyl este r conten t up to 98%. In case of he terogen eous cata lyst system ,  firstly ultras oni c was us e d to mix toge the r of oil an d m e tha nol , the n the m ixture wa s pa sse d throu gh th e s econ d ste p for ful ly trans es terif ication rea ction us ing K/A l 2 O 3 as cata lyst. Various para mete rs such as ult rasoni c mi xing tim e, reacti on tem pera ture an d am ount of cata lyst were app lied to find the optimum condition for the conve rsion of jat ropha oil to biodies el. I t wa s found tha t the meth yl es te r conte nt o ver 9 7% can be ach ieve d from a ll condition. I n a ddition, the contents of m ono-, di-, tri- gl yceride s i n biodiese l were an alyzed an d com pa red a t di fferent rea ction con di tions . Ke yw ords: Tran se st e ri ficat ion , Ultraso nic, Biodie se l, J atrop ha oil Introduc tion Rece ntly, the production of biodies el has be en increase d due to some crucial rea sons s uch a s the rise in cru deoil price, lim ite d re sou rce s of foss il oil, an d p ollution re du ction [1]. Biodies el is a n e xce lle nt sub stitute for conven tiona l di es el fue l be cause of bei ng rene wab le, n ontoxic, an d b iode gra da bl e. I t is es se nti all y sulfur- free an d e m its s ignifican tly-fewe r pa rticul ate s, un burnt hydroca rbons an d les s ca rbon oxide com pa red with con ven tiona l foss il fue ls [2,3]. The m et hod of bi odiese l m an ufacturing is b as ed on transeste rification and es te rification rea ction. Mono-al kyl es ters or biodiesel are usu all y produ ced by th e transeste rification of veg et ab le oils or a nim al f ats with m ono-alkyl alcohols. The rea ction is com m onl y carried out in the pres ence of bas e or a cid cata lysts. NaOH, K OH, Na 2 CO 3 , K 2 CO 3 , and a lkoxi de s a re used as base catalysts [4,5], while sulfonic and hydrochloric acids are often used as acid catalysts [6].  Th e con v entional biodiesel p r o duc t io n is k nown as me t ho d p r oducin g la r g e amoun t o f waste water. There fore, a ne w process u sing he teroge neous catalyst has been deve loped for environme nt- fri en dly a nd reduction of producti on cost. Several differen t h ete rogeneous ba sic ca tal ysts h ave bee n propos ed for trans es terif ication rea ction su ch a s CaO, MgO, ZnO, and Na/ γ-Al 2 O 3 e tc [3,7]. Norma lly, the reaction time of biodiesel production from homogeneous transesterification is around 30 min to 1 h de pe nding on re action tem pe rature, FFA in oil, and a m ount of cata lyst [8]. To shorte n the rea ction tim e, ultras oni c wave is one tech nique providing excellent m ixing b etween the two pha se s. It will bre ak down the liquid and form the cavitation bubbles resulting in the rising of mass transfer rate and acoustic streaming mixing [9,10]. I n th is p resen t work, the influe nce of ul tras onication on the bi odi e se l tran se ste rification rea ction for bot h hom ogeneous and heterogene ous system was studi ed over the param eters of ul tr asoni c time , am ount of cata lyst, an d rea ction tim e.

Ultrasonic on Transesterification

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7th Biomass Asia Workshop, November 29-December 01, 2010, Jakarta, Indonesia

Ultrasonic on Transesterification Reaction for Biodiesel Production

Siriporn Larpkiattaworn1*, Chalermchai Jeerapan1, Rattikan Tongpan1 , Siriporn Tongon1 

 Thailand Institute of Scientific and Technological Research (TISTR), Pathum Thani, Thailand1 Email: [email protected]

Abstract

In this work, the effect of ultrasonic on the transesterification reaction of jatropha oil to biodiesel wasstudied in both homogeneous and heterogeneous catalyst systems. All reactions were operated at 9:1methanol to oil ratio. In homogeneous catalyst system, the ultrasonic power of 1500 W and frequency of 20 kHz were applied to the mixture of hot oil (100oC) and methanol with 0.5% NaOH. The ultrasonictransesterification reaction time of 10, 20, and 30 sec were varied. It was found that at the 20 sec reactiontime, biodiesel can be produced with high methyl ester content up to 98%. In case of heterogeneouscatalyst system, firstly ultrasonic was used to mix together of oil and methanol, then the mixture waspassed through the second step for fully transesterification reaction using K/Al2O3 as catalyst. Variousparameters such as ultrasonic mixing time, reaction temperature and amount of catalyst were applied tofind the optimum condition for the conversion of jatropha oil to biodiesel. It was found that the methylester content over 97% can be achieved from all condition. In addition, the contents of mono-, di-, tri-glycerides in biodiesel were analyzed and compared at different reaction conditions.

Keywords: Transesterification, Ultrasonic, Biodiesel, J atropha oil

Introduction

Recently, the production of biodiesel has been increased due to some crucial reasons such as the

rise in crude oil price, limited resources of fossil oil, and pollution reduction [1]. Biodiesel is an excellentsubstitute for conventional diesel fuel because of being renewable, nontoxic, and biodegradable. It isessentially sulfur-free and emits significantly-fewer particulates, unburnt hydrocarbons and less carbonoxide compared with conventional fossil fuels [2,3]. The method of biodiesel manufacturing is based ontransesterification and esterification reaction. Mono-alkyl esters or biodiesel are usually produced by thetransesterification of vegetable oils or animal fats with mono-alkyl alcohols. The reaction is commonlycarried out in the presence of base or acid catalysts. NaOH, KOH, Na2CO3, K 2CO3, and alkoxides areused as base catalysts [4,5], while sulfonic and hydrochloric acids are often used as acid catalysts [6].

 The conventional biodiesel production is known as method producing large amount of wastewater. Therefore, a new process using heterogeneous catalyst has been developed for environment-friendly and reduction of production cost. Several different heterogeneous basic catalysts have been

proposed for transesterification reaction such as CaO, MgO, ZnO, and Na/γ-Al2O3 etc [3,7]. Normally,

the reaction time of biodiesel production from homogeneous transesterification is around 30 min to 1 hdepending on reaction temperature, FFA in oil, and amount of catalyst [8]. To shorten the reaction time,ultrasonic wave is one technique providing excellent mixing between the two phases. It will break downthe liquid and form the cavitation bubbles resulting in the rising of mass transfer rate and acousticstreaming mixing [9,10].

In this present work, the influence of ultrasonication on the biodiesel transesterification reactionfor both homogeneous and heterogeneous system was studied over the parameters of ultrasonic time,amount of catalyst, and reaction time.

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Experimental Procedure

Figure 1 shows the ultrasonic system that uses to enhance the mixing of jatropha oil andmethanol for both homogeneous and heterogeneous transesterification. The system is equipped withconvertor, horn, and reactor. The ultrasonic wave was generated from transducer in the convertor part

and transmitted to the horn tip to cause the cavitations in the mixture of oil and methanol. Ultrasonicpower and frequency were applied at 1500 W and 20 kHz, respectively into the reaction mixture of 9:1methanol to oil molar ratio. In this experiment, the neutralized jatropha oil was used and its properties of density, viscosity, acid value, and free fatty acid were measured.

For homogeneous transesterification system, a 100 mL of jatropha oil was heated at 100 oC andfed into the ultrasonic reactor to mix with the solution of 0.5 wt% NaOH catalyst in methanol. Theultrasonic reaction time was varied at 10, 20, and 30 sec. In the heterogeneous transesterification system,ultrasonic was used to enhance the well mixing of jatropha oil and methanol before doing the reaction inthe three-neck flask using K/Al2O3 as catalyst. Reaction temperature was controlled at 60oC with time of 0.5, 1, and 3 h. The ultrasonic mixing time was varied at 0, 10, 20, and 30 sec. Furthermore, threedifferent amounts (3.3%, 5%, and 15%) of K/Al2O3 catalyst were used for the reaction.

After reaction, glycerol was separated by gravitation and methyl ester was cleaned to remove theaccess alkali, methanol and water. Consequently, the purified methyl ester or biodiesel was measured forviscosity (Viscometer, Brookfield TC-200) and glyceride content was analyzed using GasChromatography (GC, Shimadzu GC-2010). The free fatty acid methyl ester content was analyzed usingGas Chromatography (GC, Agilent 6890N).

Figure 1. Schematic diagram of the ultrasonic transesterification system.

convertor 

reactor 

horn =

reactor

horn

convertor

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Results and Discussions

 The jatropha oil that used as feedstock in this experiment is the neutralized oil which has freefatty acid and moisture content around 0.2%, the properties of neutralized jatropha oil are shown in table1. In the homogeneous catalyst system, reaction time is set under ultrasonic irradiation which is 10, 20,

and 30 sec. The glyceride content in biodiesel is decreased with the increase of ultrasonic mixing timefrom 10 to 20 sec and it is nearly constant for the longer of ultrasonic time. Table 2 shows that usingultrasonication can produce biodiesel with glyceride content and methyl ester content ( 98%) in the rangeof EN standard at the shorten reaction time of 20 sec.

 Table 1 The properties of jatropha oil.

Density(g/ml)

Kinemetic Viscosity(cSt)

Free Fatty Acid(%)

Moisture content(%)

0.884 59.41 0.17 0.14

 Table 2 Viscosity and mono-, di-, tri-glycerides content of biodiesel obtained from ultrasonictransesterification using 0.5% NaOH catalyst, MeOH:Oil =9:1, reaction temperature 60oC.

Ultrasonic Time(Sec)

Viscosity(cSt)

Monoglyceride(%)

Diglyceride(%)

 Triglyceride(%)

 Total glycerin(%)

10 4.56 0.41 0.10 0.27 0.16520 4.49 0.43 0.06 0.17 0.15130 4.43 0.45 0.12 0.20 0.153

EN standard <5 0.8 0.2 0.2 0.25

In heterogeneous catalyst system, at first oil and methanol were mixed using ultrasound and thenK/Al2O3 catalyst was added for the reaction. Table 3 shows the value of viscosity under the change of 

catalyst amount, ultrasonic mixing time, and reaction time. It was found that catalyst amount is moreinfluential on reaction than ultrasonic mixing time and reaction time. Therefore, the amount of catalystwas fixed for the next study. By using 5% K/Al2O3 catalyst and 3h reaction time, the di- and tri-glyceridecontents are remarkably decreased when the ultrasonic mixing time is increased from 5 to 20 sec. Thelonger ultrasonic mixing time than 20 sec will present less change of glyceride content in biodiesel asshown in figure 2.

 Table 3 Viscosity of biodiesel obtained from ultrasonic mixing of MeOH:Oil =9:1 andtransesterification reaction using K/Al2O3 catalyst at 60oC.

Catalyst amount(%)

Ultrasonic Mixing Time(Sec)

Reaction Time(h)

Viscosity(cSt)

3.3 0 0.5 5.913.3 10 0.5 5.863.3 20 0.5 5.973.3 30 0.5 6.385.0 10 0.5 5.295.0 10 1.0 4.9515.0 10 0.5 4.5215.0 20 0.5 4.53

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7th Biomass Asia Workshop, November 29-December 01, 2010, Jakarta, Indonesia

 The standard biodiesel with methyl ester content over 97% can be achieved under the reactioncondition using ultrasonic mixing of oil and methanol for 20 sec, adding 15% K/Al2O3 catalyst, andoperating the reaction at 60oC for 1 h. As result shows in figure 3, by using ultrasonic mixing for 20 sec,the reaction time can be reduced to 1 h from 3 h (without ultrasonic mixing). Therefore, ultrasonicationcan effectively promote transesterification reaction of jatropha oil and reduce reaction time in

homogeneous and heterogeneous system. This is due to the cavitation effect created by ultrasonicirradiation with sufficient energy in the immiscible liquids. The micro bubbles are formed and collapserapidly, then generated the energy for chemical and mechanical effects. It is also generated themacroscopic flow in the liquid by absorption of ultrasonic wave [10].

Figure 2 Glyceride contents of biodiesel obtained from ultrasonic mixing of MeOH:Oil = 9:1 and

transesterification reaction using 5% K/Al2O3 catalyst at 60oC and reaction time 3 h.

Figure 3 Glyceride contents of biodiesel obtained from with and without ultrasonic mixing of MeOH:Oil

=9:1 and transesterification reaction at 60oC, using 15% K/Al2O3 catalyst compare to the EN standard.

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Conclusions

Biodiesel can be produced by using ultrasound to enhance the transesterification reaction for bothin homogeneous and heterogeneous systems. Ultrasonic irradiation can provide the properties of biodiesel such as viscosity and mono-, di-, tri-glyceride contents which are within the limit of EN

standard. Moreover this method could reduce the transesterification reaction time to 20 sec forhomogeneous system, and to 1h for heterogeneous system with using 15% K/Al2O3 catalyst.

References

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[2] J. Gerpen Van, Fuel Processing Technol. 86 (2005) 1097.[3] L.C. Meher, D. V. Sagar, S. N. Naik, Renewable & Sustainable Energy Reviews, 10 (2006) 248.[4] R.O. Feuge, A.T. Gros, J . Am. Oil Chem. Soc. 26 (1949) 97.[5] A. Cotevon, G. Vicente, M. Martinez, J . Aracil, Recent Res. Dev. Oil Chem. 1 (1997) 109.

[6] Y. Shimada, Y. Watanabe, T. Samukawa, A. Sugihara, H. Noda, H. Fukuda, Y. Tominaga, J . Am. OilChem. Soc. 76 (1999) 789.

[7] H.J . Kim, B. S. Kang, M. J. Kim, Y. M. Park, D. K. Kim, J.S. Lee, K.Y. Lee, Catalyst Today 93-95(2004) 315.

[8] A.K. Tiwari, A. Kumar, H. Raheman, Biomass Bioenergy, 31(2007)569.[9] T.J . Mason, Sonochemistry, Oxford University Press, New York (1999) 2.[10] J .A.Colucci, E.E. Borrero, F. Alape, JAOCS, 82;7(2005) 525.