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Reactive Extraction of Jatropha Curcas L. Seed for Production of Biodiesel Process Optimization Study

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  Reactive Extraction of   Jatrophacurcas  L. Seed for Production of Biodiesel: Process OptimizationStudy S I E W H O O N G S H U I T ,  † K E A T T E O N G L E E , *  , †  A Z L I N A H A R U N K A M A R U D D I N ,  †  A N DS U Z A N A Y U S U P  ‡ School of Chemical Engineering, Engineering Campus,Universiti Sains Malaysia, Seri Ampangan,14300 Nibong Tebal, Pulau Pinang, Malaysia, and Department of Chemical Engineering, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak, Malaysia  Received September 8, 2009. Revised manuscript received  April 20, 2010. Accepted April 27, 2010. Biodiesel from  Jatropha curcas   L. seed is conventionallyproducedviaatwo-stepmethod:extractionofoilandsubsequentesterification/transesterification to fatty acid methyl esters(FAME), commonly known as biodiesel. Contrarily, in this study,a single step in situ extraction, esterification and transesteri-fication (collectively known as reactive extraction) of  J. curcas  L. seed to biodiesel, was investigated and optimized. Designof experiments (DOE) was used to study the effect of variousprocessparametersontheyieldofFAME.Theprocessparametersstudied include reaction temperature (30 - 60  ° C), methanol to seed ratio (5 - 20 mL/g), catalyst loading (5 - 30 wt %), andreactiontime(1 - 24h).Theoptimumreactionconditionwasthenobtained by using response surface methodology (RSM)coupled with central composite design (CCD). Results showed that an optimum biodiesel yield of 98.1% can be obtainedunder the following reaction conditions: reaction temperatureof 60 ° C, methanol to seed ratio of 10.5 mL/g, 21.8 wt % of H 2 SO 4 ,and reaction period of 10 h. Introduction Owingtotheworldpetroleumcrisis,productionofbiodieselin Malaysia has increased steadily for the past three years;from325,000tonsin2006to400,000tonsin2007and420,000tons in 2008 ( 1 ). This increase is in tandem with the world’sincreasing biodiesel demand, especially in the Europeanregion. However, the practice of using edible oils, which iscurrently the most common feedstock for biodiesel produc-tion, has raised criticism from various sectors, especially nongovernmental organization (NGO), claiming that biodie-sel is competing for resources with the food industry.Therefore,productionofbiodieselfromnonedibleoilssuchas  Jatrophacurcas  L.seeds( 2  ),beeftallow( 3  ),wastecooking oil ( 4  ), and  Cerbera odollam   (sea mango) ( 5  ) would be apotentialsolutiontothisissue.Amongthesechoices,  J.curcas  L. seed has recently been hailed as the promising feedstock for biodiesel production because it can be cultivated in dry and marginal lands ( 6  ), and thus it does not compete forarable land that would have otherwise being planted withfood crops. Besides, its oil yield as shown in Table 1 iscomparabletothatofpalmoilbutmuchhigherascomparedto other edible oil crops such as rapeseed, sunflower, andsoybean( 7,8  ).Therefore,evenMalaysia,theworld’ssecondlargest palm oil producer, is now diversifying its biodieselfeedstocktowardjatropha.Thetotaljatrophaplantationareain Malaysia, at the end of 2008, was estimated at 750,000acres and is expected to increase to 1.5 million acres in 2009and 2.5 million acres in 2010 ( 9  ).Conventional methods for producing biodiesel from jatropha and other types of oil seeds involve various stages:oil extraction, purification (degumming, dewaxing, deacidi-fication, dephosphorization, dehydration, etc.), and subse-quent esterification or transesterification. These multiplebiodiesel processing stages constitute  > 70% of the totalbiodiesel production cost if refined oil is used as feedstock ( 10  ). Recently, in our previous study, it was shown that insitu extraction and esterification/transesterification, simply knownasreactiveextraction,isafeasibletechnologyfortheproduction of biodiesel using a single step that can cut theprocessingcost.Inthereactiveextractionprocess,extractionofoilandesterification/transesterificationproceedinasinglestep in which the oil-bearing material contacts with alcoholdirectly instead of reacting with pre-extracted oil. In other words, alcohol acts both as an extraction solvent and as atransesterification reagent during reactive extraction, andtherefore a higher amount of alcohol is required. However,reactiveextractioneliminatestherequirementoftwoseparateprocesses, the costly hexane oil extraction process and thetransesterificationreactionprocess,thusreducingprocessing time,cost,andamountofsolventrequired( 11 ).Furthermore,onthebasisofasimilarstudyreportedintheliterature(using soybeans), it was demonstrated that the reactive extractionprocess can be scaled up without encountering muchproblem in mass and heat transfer limitations ( 12  ).Nevertheless, in our previous study, the requirement of a24hreactiontimetoachieveahighfattyacidmethylesters(FAME) yield of 99.9% makes this process unattractive froman industrial perspective ( 11 ). Thus, the aim of this study isto optimize the process parameters of the acid-catalyzedreactiveextractionprocessfortheproductionofFAMEfrom  J. curcas   L. seed. Experimental Section Materials.  J. curcas   L. seed was purchased from Misi Bumi Alam Sdn Bhd, Malaysia. Methanol (99.9% purity) waspurchased from J. T. Baker, Germany. The remaining chemicals used in this study, sulfuric acid (H 2 SO 4 , 95 - 97%purity),methylheptadecanoate(internalstandard),andpuremethyl esters such as methyl palmitate, methyl stearate, * Correspondingauthorphone: + 604-5996467;fax: + 604-5941013;e-mail: chktlee@eng.usm.my. † SchoolofChemicalEngineering,EngineeringCampus,UniversitiSains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Pulau Pinang,Malaysia ‡ Department of Chemical Engineering, Universiti TeknologiPETRONAS, 31750 Tronoh, Perak, Malaysia TABLE 1 .  Oil Yield of   Jatropha curcas  L. Seed and OtherMajor Oil Crops oil crop oil yield (tons/ha/year) J. curcas   L. seed 2.70 ( 7  )oil palm (mesocarp) 3.62 ( 8  )rapeseed 0.68 ( 8  )sunflower 0.46 ( 8  )soybean 0.40 ( 8  ) Environ. Sci. Technol.  2010,  44,  4361–4367 10.1021/es902608v  ©  2010 American Chemical Society VOL. 44, NO. 11, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY   9 4361 Published on Web 05/10/2010  methyl oleate, and methyl linoleate, were purchased fromFluka Chemie, Germany. Pretreatment of   J. curcas   L. Seed and Oil Content. Initially, fresh  J. curcas   L. seed was blended and sieved to asizeof  < 1mm( 11 ).Itwasthenweighedanddriedintheovenat 76  ° C repeatedly until constant weight was achieved ( 13  ).Thedriedseedwasthensievedagaintoobtainfineparticlesof  e 0.355 mm in size. To determine the maximum amountof oil that can be extracted from the seed using theconventional method, a Soxhlet extractor with excess  n  -hexane as the solvent was utilized. After the extractionprocess,hexanewasremovedusingarotaryevaporator,andthe extracted oil was measured ( 11 ). This value will be usedin the calculation of yield. Reactive Extraction.  The reactive extraction to convert jatrophaseedtobiodieselwascarriedoutinaround-bottomflask equipped with a reflux system, magnetic stirrer, andheater. Initially, 20 g of jatropha seed was loaded into a 500mL round-bottom flask. Methanol and concentrated H 2 SO 4 in the ranges of 5 - 20 mL/g and 5 - 30 wt %, respectively, werethenaddedintotheround-bottomflask.Afterthat,themixturewasheatedtothedesiredtemperature(rangingfrom30 to 60  ° C) for the necessary duration (ranging from 1 to24 h). Upon completion of the reaction period, the mixture was cooled and then filtered. The solid residue was washedrepeatedly with methanol, and the excess methanol in thefiltrate was recovered using a rotary evaporator. Afterevaporation, two layers of liquid were formed. The upperlayer was dark yellow in color containing crude biodiesel, whereasthebottomlayerwasdarkbrownincolorcontaining glycerol.Thevolumeofthetoplayerwasthenmeasuredandrecorded ( 11 ). Then, the upper layer was washed with 20%NaCl solution several times until the pH became neutral. After washing, the upper layer was dried over anhydroussodium sulfate. SampleAnalysis. Thecompositionandyieldoffattyacidmethyl esters (FAME) or biodiesel in the upper layer of thereactive extraction products were analyzed using gas chro-matography(PerkinElmer,claurus500)equippedwithaflameionized detector (FID) and a Nukol capillary column (15 m × 0.53 mm; 0.5  µ m film).  n  -Hexane was used as the solvent, whereas helium was used as the carrier gas. The oventemperature was set at 110  ° C and then increased to 220  ° Cat a rate of 10 ° C/min. The temperatures of the detector andinjector were set at 220 and 250  ° C, respectively. Methylheptadecanoatewasusedastheinternalstandard.Thepeaksof different methyl esters were identified by comparing theretention time of each component in the reaction samples with the peak of pure methyl ester standard compounds.The yield of FAME in the samples was calculated as ( 11 ) Statistical Analysis and Optimization Using Design of Experiments(DOE). Theeffectofreactiveextractionprocessparameters on the yield of FAME was studied using DOE.The process parameters studied include reaction temper-ature, methanol to seed ratio, catalyst loading, and reactiontime.TheDOEselectedwasresponsesurfacemethod(RSM)coupledwithcentralcompositedesign(CCD)usingDesign-Expert version 6.0.6 (Stat-Ease, Inc.) software. Table 2indicates the coded and actual values of the processparametersused,whereasTable3showsthecompletedesignmatrix.Onthebasisofthestatisticalanalysisresult,theyieldof FAME was correlated to the process parameters with aquadraticmodelusingregressionanalysis.Itwasthenutilizedfor optimization purposes. Results and Discussion DevelopmentofRegressionModel. Table 3 shows the yieldof FAME obtained using reactive extraction with a combina-tion of various process parameters. The result was thenanalyzed using analysis of variance (ANOVA) and is showninTable4.Byeliminatingtheinsignificantparameters(valuesof“prob > F  ”of  > 0.05),multipleregressionanalysisgivesthefollowing quadratic model equation (in coded factors) thatcorrelates the yield of FAME to the various processparameters: As shown in Table 4, the  F   test (Fisher) on eq 2 gives an F   value of 21.8 and a “prob  >  F  ” value of   < 0.0001, indicating thatthedevelopedmodelissignificant.Besidesthat, R  2 shownin Table 4 is very close to unity, 0.9532, indicating that thedeveloped model equation successfully captured the cor-relationbetweentheprocessparameterstotheyieldofFAMEfor reactive extraction process of jatropha seed. Effect of Single Process Parameter.  On the basis of theresultsshowninTable4,allfourprocessparametersstudied,reactiontime(  A  ),reactiontemperature( B  ),methanoltoseedratio( C  ),andcatalystloading( D  ),werefoundtosignificantly affect the yield of FAME because their  F   values are higherthanthetheoreticalvalue, F  1,15 of4.54atthe95%confidenceinterval. THe parameter with the highest  F   value will havethe most significant effect. Thus, by referring to Table 4, theparameter with the most significant effect on the yield of FAME in descending order is catalyst (H 2 SO 4 ) loading,followed by reaction temperature, reaction time, and finally methanoltoseedratio.Apartfromthat,thepositivesignforallfourregressioncoefficients(  A  , B  , C  ,and D  )ineq2indicatesapositiveeffectontheyieldofFAME.ThesefindingscanbeeasilyverifiedbyvisuallyinspectingtheexperimentalresultsshowninTable3.Forexample,bycomparisonbetweenruns2 and 7 (and other comparable runs), an increase in H 2 SO 4 loadingcausedavastincreaseintheyieldofFAME.Asimilarfinding can be made for the effect of reaction temperature(e.g.,runs6and22).However,forreactiontime(runs20and25) and methanol to seed ratio (runs 3 and 13), increases intheseparameterscausedonlyaslightincrementintheyieldof FAME.Figure 1 shows the effect of reaction time on the yield of FAME. As shown in Figure 1, the yield of FAME increased with higher reaction time. In our previous study, it wasreportedthatthelimitingfactorforreactiveextractionprocess TABLE 2 .  Coded and Actual Values of Process Parameters in Central Composite Design levelvariable code unit  - 2 ( -r  )  - 1 0  + 1  + 2 ( +r  ) reaction time  A  h 1 7 13 18 24reaction temperature  B   ° C 30 38 45 53 60methanol to seed ratio  C   g/mL 5 8.75 12.5 16.25 20H 2 SO 4  loading  D   wt % 5 11.25 17.5 23.75 30  yield (%)  ) ( Σ concn of each component)  ×  (vol of upper layer)total wt of oil in sample  ×  100%(1) yield (wt %)  )  58.6  +  10.2  A   +  16.8 B   +  9.11 C   +  18.5 D   - 5.34  A  2 -  4.28 D  2 +  5.63 BD   (2) 4362  9  ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 11, 2010  is the leaching of oil from the seed itself ( 11 ). Therefore,sufficienttimewillberequiredtoleachtheoilfromtheseedand subsequently be transesterified to FAME. From Figure2, the yield of FAME was found to increase linearly withreaction temperature in agreement with those reported inthe literature ( 14, 15  ). This can be easily justified as highertemperature can increase the extraction rate of oil fromthe seed and, in addition, the endothermic nature of thetransesterificationreactionwillshiftthereactiontowardtheforward direction at higher reaction temperature ( 16  ). It isnoted here that in this study, the reaction temperature islimited to 60 ° C so that this process can be comparable withtheconventionalbase-catalyzedtransesterificationreaction.The role of methanol in reactive extraction is not only asanextractionsolventbutalsoasatransesterificationreagent.Therefore, the requirement of methanol in this particularprocess is higher than in other conventional transesterifi-cationreaction.AsshowninFigure3,theyieldofFAMEwasfoundtoincreaselinearlywithhighermethanoltoseedratio.This is because with a higher amount of methanol, theconcentration gradient to leach oil from the seed will belarger.Furthermore,theexcessamountofmethanolwilldrivethetransesterificationreactionforwardtowardtheformationof FAME. However, it was found that the effect of methanolto seed ratio on the yield of FAME is least significant among the four process parameters studied as indicated by the TABLE 3 .  Experiment Matrix with Coded Factors of CCD and Response run A , reaction time (h) B  , reaction temperature ( ° C) C  , methanol toseed ratio (g/mL) D  , catalystloading (wt %) yield (%) 1 13 45 12.50 5.00 4.232 7 38 16.25 11.25 19.203 18 53 16.25 11.25 60.764 13 45 5.00 17.50 30.205 7 53 8.75 11.25 16.826 13 60 12.50 17.50 99.547 7 38 16.25 23.75 48.588 7 38 8.75 23.75 29.659 7 38 8.75 11.25 1.7510 7 53 16.25 23.75 86.2411 18 53 8.75 23.75 90.9312 18 53 16.25 23.75 94.7813 18 53 8.75 11.25 52.2714 18 38 8.75 23.75 40.6815 18 38 8.75 11.25 22.2216 1 45 12.50 17.50 15.5417 7 53 8.75 23.75 70.1518 13 45 20.00 17.50 93.1919 7 53 16.25 11.25 28.7520 24 45 12.50 17.50 68.4021 13 45 12.50 30.00 88.1722 13 30 12.50 17.50 28.0023 18 38 16.25 11.25 30.6524 18 38 16.25 23.75 48.29repeated experiments25 13 45 12.50 17.50 60.8326 13 45 12.50 17.50 60.4527 13 45 12.50 17.50 56.6628 13 45 12.50 17.50 60.3929 13 45 12.50 17.50 53.2330 13 45 12.50 17.50 60.13 TABLE 4 .  ANOVA for Response Surface Quadratic Model for the Yield of FAME source sum of squares DF mean square  F   value prob  >  F  model 21688.99 14 1549.21 21.84  < 0.0001 a  A  2504.31 1 2504.31 35.30  < 0.0001 a  B   6758.98 1 6758.98 95.27  < 0.0001 a  C   1994.00 1 1994.00 28.11  < 0.0001 a  D   8242.14 1 8242.14 116.18  < 0.0001 a  A 2 788.11 1 788.11 11.01 0.0047 a  B  2 0.35 1 0.35 0.004984 0.9447 b  C  2 4.5 1 4.5 0.063 0.8045 b  D  2 502.2 1 502.2 7.08 0.0178 a  AB   183.06 1 183.06 2.58 0.1290 b  AC   81.09 1 81.09 1.14 0.3019 b  AD   219.93 1 219.93 3.10 0.0987 b  BC   9.09 1 9.09 0.13 0.7254 b  BD   507.6 1 507.6 7.15 0.0173 a  CD   0.002025 1 0.002025 0.00002854 0.9958 b  residual 1064.19 15 70.95 R  2 )  0.9532; adjusted  R  2 )  0.9096; predicted  R  2 )  0.7394; standard deviation  )  8.42; mean  )  50.69 a  Significant at 95% confident interval.  b  Not significant at 95% confident interval. VOL. 44, NO. 11, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY   9  4363  smallest  F   value shown in Table 4. This is probably becauseevenatthelowerrangeofmethanoltoseedratiousedinthisstudy ( 5  ), there is already sufficient methanol to create theconcentration gradient required to leach oil from the seed. As mentioned in the earlier section, catalyst (H 2 SO 4 )loadingwasfoundtohavethemostsignificantpositiveeffecton the yield of FAME among all four reaction parameters.FromFigure4,itcanbeseenthatahigheramountofcatalystused will increase the yield of FAME significantly. Forinstance,whentheamountofH 2 SO 4 inthereactionmixture was set at a minimum level of 5 wt % (run 1), the yield of FAME was merely 4.23%; however, at a higher amount of catalyst of 30 wt % (run 21) the yield increased significantly to88.2%.ThisisbecauseH 2 SO 4 playstheroleofcatalystnotonlyinthereactiveextractionprocessbutalsoinaccelerating the extraction of oil from jatropha seed as it was reportedthat lipid or oil dissolved better in acidic solvent ( 17  ).Therefore,byincreasingtheamountofH 2 SO 4 inthereactionmixture, more oil can be extracted more quickly and easily and be transesterified to FAME. The acidic nature of theproductmixtureduetousageofH 2 SO 4 canbeeasilyovercome FIGURE 1. Individual effect of reaction time on FAME yield inreactive extraction of  Jatropha   seed.FIGURE 2. Individual effect of reaction temperature on FAMEyield in reactive extraction of  Jatropha   seed.FIGURE 3. Individual effect of methanol to seed ratio on FAMEyield in reactive extraction of  Jatropha   seed.FIGURE 4. Individual effect of catalyst loading on FAME yieldin reactive extraction of  Jatropha   seed.FIGURE 5. Interaction effect between reaction temperature andcatalyst loading on FAME yield shown as (a) a three-dimensionalplot and (b) a two-dimensional plot. 4364  9  ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 44, NO. 11, 2010

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