research article kinetic study on the cs h pw o /fe-sio...

Hindawi Publishing CorporationThe Scientific World JournalVolume 2013 Article ID 612712 6 pageshttpdxdoiorg1011552013612712

Research ArticleKinetic Study on the Cs

119883H3minus119883

PW12

O40

Fe-SiO2

Nanocatalyst forBiodiesel Production

Mostafa Feyzi12 Leila Norouzi1 and Hamid Reza Rafiee1

1 Faculty of Chemistry Razi University PO Box 6714967346 Kermanshah Iran2Nanoscience amp Nanotechnology Research Center (NNRC) Razi University PO Box 6714967346 Kermanshah Iran

Correspondence should be addressed to Mostafa Feyzi dalahoo2011yahoocom

Received 2 September 2013 Accepted 20 October 2013

Academic Editors H Choi and D Fu

Copyright copy 2013 Mostafa Feyzi et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The kinetic of the transesterification reaction over the Cs119883H3minus119883

PW12O40Fe-SiO

2catalyst prepared using sol-gel and impregnation

procedures was investigated in different operational conditions Experimental conditions were varied as follows reactiontemperature 323ndash333K methanoloil molar ratio = 121 and the reaction time 0ndash240min The H

3PW12O40

heteropolyacid hasrecently attracted significant attention due to its potential for application in the production of biodiesel in either homogeneousor heterogeneous catalytic conditions Although fatty acids esterification reaction has been known for some time data is stillscarce regarding kinetic and thermodynamic parameters especially when catalyzed by nonconventional compounds such asH3PW12O40 Herein a kinetic study utilizing Gc-Mas in situ allows for evaluating the effects of operation conditions on reaction

rate and determining the activation energy along with thermodynamic constants including ΔG ΔS and ΔH It indicated that theCs119883H3minus119883

PW12O40Fe-SiO

2magnetic nanocatalyst can be easily recycled with a little loss bymagnetic field and canmaintain higher

catalytic activity and higher recovery even after being used 5 times Characterization of catalyst was carried out by using scanningelectronmicroscopy (SEM) X-ray diffraction (XRD) Fourier transform-infrared spectroscopy (FT-IR) N

2adsorption-desorption

measurements methods thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC)

1 Introduction

Biodiesel is a fuel composed ofmonoalkyl esters of long chainfatty acids derived from renewable sources such as vegetableoils and animal fats [1] Due to oxygen content biodiesel isa clean nontoxic and biodegradable fuel with low exhaustemissions without the sulphur and carcinogen content [2]Biodiesel is prepared via reaction between triglycerides andalcohol in the presence of a catalyst [3] Transesterificationreaction of oil and alcohol with homogeneous catalyst is themost commonmethod for the preparation of biodiesel [4 5]However the homogeneous catalyst has many drawbackssuch as the difficulty in product separation and equipmentcorrosion requirement of large quantity of water environ-mental pollution [6] The use of heterogeneous catalyststo replace homogeneous ones is easily regenerated andhas a less corrosive nature leading to safer cheaper andmore environment-friendly operations [7] Currently theresearch is focused on sustainable solid acid catalysts for

transesterification reaction In addition it is believed thatsolid acid catalysts have the strong potential than liquid acidcatalyst [8] HPWcatalyst is a strong Broslashnsted acid with highthermal stability and high solubility in polar solvents and ithas shown to be more active in FFA esterification reactionsthan mineral acid catalysts [8ndash12] However heteropolyacidshave low surface areas and high solubility in polar solventsThese features make some difficulties in catalyst recovery andcatalyst lifetime [13]Therefore salts ofHPAswith large singlevalence ions such as Cs+ NH

4

+ and Ag+ have attractedmuch fondness because these salts will increase in surfacearea and profound changes in solubility over the parentheteropolyacid [14 15] HPW can be supported on severalkinds of support such as SiO

2 Al ZrO

2 activated carbon

SiO2-Al andMCM-41 that SiO

2is cheap easily available and

easily surface modifiable [16ndash18]In the present kinetic study pseudo-first-order model

was applied to correlate the experimental kinetic data ofcatalytic performance of the Cs

119883H3minus119883

PW12O40Fe-SiO

2for

2 The Scientific World Journal

sunflower oil transesterification with methanol and the mainthermodynamic parameters such as the effects of temperatureon reaction rate activation energy entropy variation (Δ119878)and enthalpy variation (Δ119867) were determined moreoverthe effects of temperature on reaction rate and the orderof reaction were assessed Characterization of catalyst wascarried out by using scanning electron SEM XRD FT-IR N

2

adsorption-desorption measurements methods TGA andDSC methods

2 Experimental

21 Fe-SiO2Support Preparation All materials with analyt-

ical purity were purchased from Merck and used withoutfurther purification Ferric nitrate (Fe(NO

3)3sdot9H2O) and

tetraethyl orthosilicate (TEOS) were selected as the sourceof ferric and silica respectively A typical procedure for thepreparation of ferric-silica mixed oxide containing 60wtferric was followed Firstly 30mL TEOS was mixed with cer-tain amount anhydrous ethyl alcohol (C

2H5OH) Secondly

35234 gr Fe(NO3)3sdot9H2Owas dissolved with certain amount

of anhydrous ethyl alcohol under stirring also 30 gr of oxalicacid was dissolved in certain amount of anhydrous alcoholunder stirring In the final step Fe and Si sols and oxalic acidwere added simultaneously into the beaker under constantstirring to obtain a gel form After the end of the aboveoperations the samples were aged for 90min at 50∘C Theobtained gel was dried in an oven (120∘C 12 h) to give amaterial denoted as the catalyst precursor Finally the catalystprecursor was calcined at 600∘C for 6 h to produce magneticsolid catalyst The Fe-SiO

2supported 12-tungstophosphoric

acid catalyst with 4wt of aqueous solution HPW (basedon the Fe-SiO

2weight) were prepared by incipient wetness

impregnationThe impregnated precursor was dried at 120∘Cfor overnight and calcined at 600∘C for 6 h

Finally the promoted catalyst by Cs was synthesized withCsH3PW12O40= 2wtThe salt obtained by this procedure

will be designated hereinafter as Cs119883H3minus119883

PW12O40Fe-SiO

2

where 119883 is the amount of protons per [PW12O40]3minus anion in

the salt

22 Characterization of Catalyst

221 N2Physisorption Measurements The specific surface

area total pore volume and the mean pore diameter weremeasured using a N

2adsorption-desorption isotherm at

liquid nitrogen temperature (minus196∘C) using a NOVA 2200instrument (Quantachrome USA) Prior to the adsorption-desorption measurements all the samples were degassed at110∘C in a N

2flow for 2 h to remove the moisture and other

adsorbates

222 Scanning Electron Microscopy (SEM) Themorphologyof catalyst and precursor was observed by means of an S-360Oxford Eng scanning electron microscopy

223 Fourier Transform-Infrared Spectroscopy (FT-IR)Fourier transform infrared (FT-IR) spectra of the samples

were obtained using a Bruker Vector 22 spectrometer in theregion of 400ndash4000 cmminus1

224 X-Ray Diffraction (XRD) X-ray diffraction (XRD)patterns of the catalysts were recorded on a diffractometerusing CuK

120572radiation The intensity data were collected over

a 2120579 range of 15ndash75

225 Thermal Gravimetric Analysis (TGA) and DifferentialScanning Calorimetry (DSC) The TGA and DSC were car-ried out using simultaneous thermal analyzer (PerkinElmer)under a flow of dry air with a flow rate of 50mLminminus1The temperature was raised from 20 to 700∘C using a linearprogrammer at a heating rate of 3∘Cminminus1

23 Catalytic Tests The type and quantity of methyl estersin the biodiesel samples were determined using gas chroma-tography-mass spectrometry (GC Agilent 6890N model andMass Agilent 5973N model) equipped with a flame ionizeddetector (FID) A capillary column (HP-5) with columnlength (60m) inner diameter (025mm) and 025 120583m filmthickness was used with helium as the carrier gas The tem-perature program for the biodiesel samples started at 50∘Cand ramped to 150∘Cat 10∘Cminminus1The temperaturewas heldat 150∘C for 15min and ramped to 280∘C at 5∘Cminminus1 Theholding time at the final temperature (250∘C)was 5min Alsothe injector was used from kind splitsplitless

24 Kinetic Studies The transesterification of sunflower oilwas carried out in a round bottomed flask fitted with acondenser andmagnetic stirring systemThe reaction systemwas heated to selected temperature in 50 55 and 60∘CWhenthe oil reached selected temperature methanoloil molarratio = 121 and the catalyst amount (3 wt related to oilweight) were addedwith continuous stirring (500 rpm) Aftercompletion of the reaction time (0ndash240min) the sampleconcentration is calculated according to mole fraction at anytime The results can be seen in Table 1

3 Kinetic Model

The mole fraction for the transesterification reaction wasestablished For the reaction stoichiometry requires 3Mol ofmethanol (M) and 1mol of triglyceride (TG) to give 3molof methyl ester (ME) and 1Mol of glycerol (GL) Transes-terification reaction comprises three consecutive reversiblereactions where 1mol of ME is produced in each step andmonoglycerides (MG) and diglycerides (DG) are intermedi-ate products [19]The kineticmodel used in this work is basedon the following assumptions

(1) Firstly 119896eq should be considered not to dependon methanol concentration (due to its excess) (thereaction is considered pseudo-first order [20 21])

(2) Production of intermediate species is negligible (theresult reaction is a one step)

(3) The chemical reaction occurred in the oil phase

The Scientific World Journal 3

Table 1 Concentration of methyl ester (based on mole fraction) at temperatures of 60 (A) 55 (B) and 50∘C (C) respectively

Reaction time (s) 119883ME minusln (1 minus 119883ME)A B C A B C

0 000 000 000 0000000 0000000 000000030 032 024 014 0385660 0274437 015082360 040 028 015 0510826 0328504 016251990 042 034 024 0590000 0415515 0274437120 05819 043 030 0872035 0562119 0356675150 063 051 034 0994252 0713350 0415515180 070 057 038 1203973 0843970 0478036210 075 063 045 1386294 0994252 0597837240 081 065 050 1660731 1049822 0693147119883ME concentration of methyl esterminusln (1 minus 119883ME) triglyceride concentration

Based on assumption (1)

minus119903 =

minus119889 [119879119866]

119889119905

= 119896 [119879119866] [ROH]3 (1)

And based on assumption (2)

119896

1015840= 119896[ROH]3

minus119903 =

minus119889 [119879119866]

119889119905

= 119896

1015840[119879119866]

997904rArr ln1198791198660minus ln119879119866 = 1198961015840 sdot 119905

(2)

According to the mass balance

119883ME = 1 minus[119879119866]

[119879119866

0]

[119879119866] = [1198791198660] [1 minus 119883ME]

119889119883ME119889119905

= 119896

1015840[1 minus 119883ME] 997904rArr minus ln (1 minus 119883ME) = 119896

1015840sdot 119905

(3)

Based on this model and the experimental data at first wecalculated the concentration of methyl ester at different times(based on the moles fraction) Second the rate constants ateach temperature were obtained Third the preexponentialfactors and activation energies are obtained by plotting thelogarithm of the rate constants (119896) versus 1119879 of absolutetemperature using the Arrhenius equation and in the finalstage thermodynamic parameters were obtained such as Δ119878and Δ119867

4 Results and Discussion

41 Characterization of the Catalyst The FT-IR spectra ofH3PW12O40 Cs119883PW12O40

and Cs119883H3minus119883

PW12O40Fe-SiO

2

are shown in Figure 1TheKeggin anion of HPW consists of acentral phosphorous atom tetrahedrally coordinated by fouroxygen atoms and surrounded by twelve octahedral WO

6

units that share edges and corners in the structurebandsrelated to a Keggin structure (i(OndashPndashO) = 550 cmminus1 indica-tive of the bending of the central oxygen of PndashOndashP ]as(WndashOendashW) at 798 cmminus1 related to asymmetric stretching of

001020304050607

0 500 1000 1500 2000 2500 3000

Tran

smitt

ance

()

Wavenumber (cmminus1)

(a)

(b)

(c)

Figure 1 FT-IR spectrums of the Cs119883H3minus119883

PW12O40Fe-SiO

2(a)

H3PW12O40(b) and Cs

119883H3minus119883

PW12O40(c) nanocatalysts

tungsten with edge oxygen in WndashOndashW ]as(WndashOcW) =893 cmminus1 related to the asymmetric stretching of corneroxygen in WndashOndashW ]as(W=O) = 983 cmminus1 indicative of theasymmetric stretching of the terminal oxygen and ](PndashO) at1080 cmminus1 assigned to asymmetric stretching of oxygen witha central phosphorous atom) [22 23] HPA salts maintaintheir corner Keggin structure with the addition of differentamount ofmetallic CsWhenCs

119883H3minus119883

PW12O40is supported

on Fe-SiO2 these bands have somewhat changed The bands

at 1080 and 890 cmminus1 are overlapped by the characteristicband of SiO

2 while these bands at 985 and 794 cmminus1 shift to

966 and 805 cmminus1 respectivelyThe XRD pattern of Cs

119883H3minus119883

PW12O40Fe-SiO

2catalyst

was presented in Figure 2 Supported HPA samples do notshow diffraction patterns probably due to the followingreasons (i) after treatment at 500∘C the HPA practicallyloses its crystalline structure (ii) HPA species were highlydispersed and (iii) the deposited amount of HPA was not bigenough to be detected by this technique [24]

The TGA-DSC experiment on the catalyst precursor hasshown four steps of mass loss (Figure 3) The first step at thetemperature of 70ndash110∘C was attributed to the evaporationof residual moistures in the catalyst precursor and loss ofphysisorbed waters The second stage (190ndash280∘C) is accom-panying weight loss of the crystallization water expelling


Inte

nsity

(au

)

(2 120579)20 30 40

(b)

(a)

50 60

Figure 2 XRD patterns of the Cs1H2PW12O40Fe-SiO

2(a) and

Cs1H2PW12O40(b) nanocatalysts

70

60

50

40

30

20

10

00 100 200 300 400 500 600 700

Wt loss ()Heat flow (mcals)Weight (mg)

Wt l

oss (

)

Hea

t flow

(mca

ls)

Wei

ght (

mg)

18

16

14

12

10

8

6

Temperature (∘C)

Figure 3 TGA and DSC curves for Cs119883H3minus119883

PW12O40Fe-SiO

2

precursor

which is most likely the hydrated proton The peak around390ndash460∘C is due to the decomposition of iron and Si oxalatesto oxide phases Most of weight loss happened from 580∘C to640∘C due to the phase transition and formation of Fe

2SiO4

(cubic) The weight loss curve is involved with a total overallweight loss of ca 69wt DSC measurement was performedin order to provide further evidence for the presence of thevarious species and evaluate their thermal behavior As shownin Figure 3 the endothermic curve represents the removal ofthe physically adsorbed water from the material (70ndash110∘C)Two exothermic peaks at around 190ndash280∘C and 390ndash480∘Care due to the crystallization water expelling which is mostlikely the hydrated proton and the decomposition of iron andSi oxalates to oxide phases respectivelyThe exothermic peakat around 580ndash640∘C is due to formation of iron silicate phase[25]

Figure 4 shows SEM pictures of the precursor (a) andcalcined catalyst (b) After calcination catalyst particle aggre-gated together and formed a spherical shape and moreuniform particles which are beneficial to the activity andaugmenting the surface of the catalyst that exhibited a largeamount of aggregates than the precursor The measured BETsurface areas are 2375m2 cm3 gminus1 for Cs

119883H3minus119883

PW12O40Fe-

SiO2

catalyst and corresponded pore volume is 07672cm3 gminus1 obtained from analysis of the desorption usingthe BJH (Barrett-Joyner-Halenda) method The particle sizecould be calculated by Scherer-equation form XRD pattern(Figure 2) It is clear that the catalyst particle size wasin nanodimension (45 nm) The Cs

119883H3minus119883

PW12O40Fe-SiO

2

catalyst was characterized with SEM (Figure 4) It is obviousin this figure that the crystal sizes were from 38ndash47 nm Thisresult confirmed the obtained results studied by using theScherrer equation

42 Calculation of Rate Constant Activation Energy andPreexponential Factor Plots of minus ln(1 minus 119883ME) versus (119879) aregiven in Figure 5 Rate constant has been calculated usingFigure 5 And activation energy is calculated through theArrhenius equation

119896 = 119860119890

minus119864119886119877119879 (4)

997904rArr ln 119896 = ln119860 minus119864

119886

119877119879

(5)

where (119896) is the reaction constant 119860 is the frequency or pre-exponential factor 119864

119886is the activation energy of the reaction

119877 is the gas constant and 119879 is the absolute temperatureTherefore plots of ln 119896 versus 1119879 are given in Figure 6

Activation energy (119864119886) and preexponential factor have been

calculated using Figure 6 to be 79805 kJmol and 89 times108 kJmol respectively Based on the proposed kineticmodel the kinetic parameters for this catalyst were deter-mined The experiments demonstrate that the reactionsfollow first-order kinetics The proposed kinetic modeldescribes the experimental results well and the rate constantsfollow the Arrhenius equation

43 Thermodynamic Parameters (Δ119878 and Δ119867) Based on thedefinition of Gibbs energy free using (7) and using linear plotof ln 119896eqversus ln 1119879 which is given in Figure 7 and by using(7) the respective values of Δ119878 and Δ119867were calculated whichare 00197 kJmol 79784 kJKmol respectively

Δ119866 = minus119877119879 ln 119896eq (6)

ln 119896eq =Δ119878

119877

minus

Δ119867

119877119879

(7)

From the results (Table 2) of the thermodynamic parametersit can be found that the transesterification reaction is anendothermic reaction andwith increasing temperature reac-tion rate increases Moreover enthalpy and entropy changeare not affected by methanol concentration due to its excess[26]


(a) (b)

Figure 4 The SEM images of CsXH3minusXPW12O40Fe-SiO2 nanocatalyst (a) precursor and (b) calcined catalyst

002040608

112141618

0 50 100 150 200 250 300Time (min)

y = 00066x + 00836

R2 = 09908y = 00044x + 00473

R2 = 09918

y = 00027x + 00219

R2 = 09875

minusln

(1minusX

)

Figure 5 Plots of minus ln(1 minus119883) versus time (min) at temperatures 6055 and 50∘C for reaction of sunflower oil with methanol

Table 2 Calculated values of thermodynamic parameters

T (K) Δ119866 (kJKsdotmol) Δ119867 (kJKsdotmol) Δ119878 (KJmol)323 2683272328 2598118 79784 00197333 2519303

5 Conclusions

The magnetic Cs119883H3minus119883

PW12O40Fe-SiO

2nanocatalyst was

prepared for biodiesel production Experimental conditionswere varied as follows reaction temperature 328ndash338Kmethanoloil molar ratio = 121 and the reaction time0ndash240min Thermodynamic properties such as Δ119878 andΔ119867 were successfully determined from equilibrium con-stants measured at different temperature Activation energy(119864119886) and preexponential factor have been calculated to

be 79805 kJmol and 89 times 108 kJmol respectively Theexperiments demonstrate that the reactions follow first-orderkinetics Also notably recovery of the catalyst can be achievedeasily with the help of an external magnet in a very short time(lt20 seconds)with noneed for expensive ultracentrifugation

0003 000304 000308minus91

minus92

minus93

minus94

minus95

minus96

minus97

minus98

minus99

minus10

minus101

y = minus96151x + 19763

R2 = 09998

1T

lnk

Figure 6 Arrhenius plot of ln 119896 versus 1119879 for reaction of sunfloweroil with methanol

25000

25600

26200

26800

322 327 332

y = minus16397x + 79784

R2 = 09995

ΔG (JKmiddotmol)

ΔG

(JK

middotmol

)

T (K)

Figure 7 Plot ofΔ119866 (JKsdotmol) versus119879 (K) for reaction of sunfloweroil with methanol

Acknowledgment

Theauthors are grateful to the IranNanotechnology InitiativeCouncil (INIC) for its partial support of this project


References

[1] M CMath S P Kumar and S V Chetty ldquoTechnologies for bio-diesel production from used cooking oil a reviewrdquo Energy forSustainable Development vol 14 no 4 pp 339ndash345 2010

[2] P-L Boey G P Maniam and S A Hamid ldquoPerformance ofcalcium oxide as a heterogeneous catalyst in biodiesel produc-tion a reviewrdquo Chemical Engineering Journal vol 168 no 1 pp15ndash22 2011

[3] E H Pryde ldquoVegetable oils as fuel alternatives symposiumoverviewrdquo Journal of the American Oil Chemists Society vol 61no 10 pp 1609ndash1610 1984

[4] J M Dias M C M Alvim-Ferraz and M F Almeida ldquoCom-parison of the performance of different homogeneous alkalicatalysts during transesterification of waste and virgin oils andevaluation of biodiesel qualityrdquo Fuel vol 87 no 17-18 pp 3572ndash3578 2008

[5] Z Helwani M R Othman N Aziz J Kim and W J N Fern-ando ldquoSolid heterogeneous catalysts for transesterification oftriglycerides with methanol a reviewrdquo Applied Catalysis A vol363 no 1-2 pp 1ndash10 2009

[6] L C Meher D Vidya Sagar and S N Naik ldquoTechnical as-pects of biodiesel production by transesterification a reviewrdquoRenewable and Sustainable Energy Reviews vol 10 no 3 pp248ndash268 2006

[7] F Qiu Y Li D Yang X Li and P Sun ldquoThe use of heteroge-neous catalysts to replace homogeneous ones can be expected toeliminate the problems associatedwith homogeneous catalystsrdquoBioresource Technology vol 102 pp 4150ndash4156 2011

[8] K Jacobson R Gopinath L C Meher and A K Dalai ldquoSolidacid catalyzed biodiesel production from waste cooking oilrdquoApplied Catalysis B vol 85 no 1-2 pp 86ndash91 2008

[9] M Zabeti W M A Wan Daud and M K Aroua ldquoActivity ofsolid catalysts for biodiesel production a reviewrdquo Fuel Process-ing Technology vol 90 no 6 pp 770ndash777 2009

[10] S Shanmugam B Viswanathan and T K Varadarajan ldquoEsteri-fication by solid acid catalysts a comparisonrdquo Journal of Molec-ular Catalysis A vol 223 no 1-2 pp 143ndash147 2004

[11] Y Liu E Lotero and J G Goodwin Jr ldquoA comparison of theesterification of acetic acid with methanol using heterogeneousversus homogeneous acid catalysisrdquo Journal of Catalysis vol242 no 2 pp 278ndash286 2006

[12] Z Helwani M R Othman N Aziz W J N Fernando and JKim ldquoTechnologies for production of biodiesel focusing ongreen catalytic techniques a reviewrdquo Fuel Processing Technologyvol 90 no 12 pp 1502ndash1514 2009

[13] H-J Kim Y-G Shul and H Han ldquoSynthesis of heteropolyacid(H3PW12O40)SiO

2nanoparticles and their catalytic proper-

tiesrdquo Applied Catalysis A vol 299 no 1-2 pp 46ndash51 2006[14] N Mizuno and M Misono ldquoPore structure and surface area of

Cs (x = 0ndash3 M = W Mo)rdquo Chemistry Letters vol 16 pp 967ndash970 1987

[15] T Okuhara T Ichiki K Y Lee and M Misono ldquoDehy-dration mechanism of ethanol in the pseudoliquid phase ofH3minus119883

Cs119883PW12O40rdquo Journal ofMolecular Catalysis A vol 55 pp

293ndash301 1989[16] L R Pizzio P G Vazquez C V Caceres et al ldquoC-alkylation

reactions catalyzed by silica-supported Keggin heteropoly-acidsrdquo Applied Catalysis A vol 287 no 1 pp 1ndash8 2005



tiesrdquo Applied Catalysis A vol 299 no 1-2 pp 46ndash51 2006

[18] X Zhao Y Han X Sun and Y Wang ldquoStructure and catalyticperformance of H

3PW12O40SiO2prepared by several meth-

odsrdquo Chinese Journal of Catalysis vol 28 no 1 pp 91ndash96 2007[19] Q Shu J Gao Y Liao and J Wang ldquoReaction kinetics of bio-

diesel synthesis from waste oil using a carbon-based solid acidcatalystrdquo Chinese Journal of Chemical Engineering vol 19 no 1pp 163ndash168 2011

[20] S Saka and D Kusdiana ldquoBiodiesel fuel from rapeseed oil asprepared in supercritical methanolrdquo Fuel vol 80 no 2 pp 225ndash231 1998

[21] D Kusdiana and S Saka ldquoKinetics of transesterification in rape-seed oil to biodiesel fuel as treated in supercritical methanolrdquoFuel vol 80 no 5 pp 693ndash698 2001

[22] K Srilatha R Sree B L A Prabhavathi Devi P S S PrasadR B N Prasad and N Lingaiah ldquoPreparation of biodieselfrom rice bran fatty acids catalyzed by heterogeneous cesium-exchanged 12-tungstophosphoric acidsrdquo Bioresource Technol-ogy vol 116 pp 55ndash57 2012

[23] L Nakka J E Molinari and I E Wachs ldquoSurface and bulkaspects of mixed oxide catalytic nanoparticles oxidation anddehydration of CH

3OH by polyoxometallatesrdquo Journal of the

American Chemical Society vol 131 no 42 pp 15544ndash155542009

[24] J C Yori J M Grau V M Benıtez and J Sepulveda ldquoHydro-isomerization-cracking of n-octane on heteropolyacidH3PW12O40

supported on ZrO2 SiO

2and carbon Effect of

Pt incorporation on catalyst performancerdquo Applied Catalysis Avol 286 no 1 pp 71ndash78 2005

[25] Q Deng W Zhou X Li et al ldquoMicrowave radiation solid-phase synthesis of phosphotungstate nanoparticle catalystsand photocatalytic degradation of formaldehyderdquo Journal ofMolecular Catalysis A vol 262 no 1-2 pp 149ndash155 2007

[26] S A Fernandes A L Cardoso and M J Da Silva ldquoA novelkinetic study of H

3PW12O40 catalyzed oleic acid esterification

with methanol via HNMR spectroscopyrdquo Fuel Processing Tech-nology vol 96 pp 98ndash103 2012

TribologyAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FuelsJournal of


Journal ofPetroleum Engineering


Industrial EngineeringJournal of


Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

CombustionJournal of


Journal of


Renewable Energy

Submit your manuscripts athttpwwwhindawicom


StructuresJournal of


RotatingMachinery


EnergyJournal of


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Nuclear InstallationsScience and Technology of


Solar EnergyJournal of


Wind EnergyJournal of


Nuclear EnergyInternational Journal of


High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


sunflower oil transesterification with methanol and the mainthermodynamic parameters such as the effects of temperatureon reaction rate activation energy entropy variation (Δ119878)and enthalpy variation (Δ119867) were determined moreoverthe effects of temperature on reaction rate and the orderof reaction were assessed Characterization of catalyst wascarried out by using scanning electron SEM XRD FT-IR N

2

adsorption-desorption measurements methods TGA andDSC methods

2 Experimental

21 Fe-SiO2Support Preparation All materials with analyt-

ical purity were purchased from Merck and used withoutfurther purification Ferric nitrate (Fe(NO

3)3sdot9H2O) and

tetraethyl orthosilicate (TEOS) were selected as the sourceof ferric and silica respectively A typical procedure for thepreparation of ferric-silica mixed oxide containing 60wtferric was followed Firstly 30mL TEOS was mixed with cer-tain amount anhydrous ethyl alcohol (C

2H5OH) Secondly

35234 gr Fe(NO3)3sdot9H2Owas dissolved with certain amount

of anhydrous ethyl alcohol under stirring also 30 gr of oxalicacid was dissolved in certain amount of anhydrous alcoholunder stirring In the final step Fe and Si sols and oxalic acidwere added simultaneously into the beaker under constantstirring to obtain a gel form After the end of the aboveoperations the samples were aged for 90min at 50∘C Theobtained gel was dried in an oven (120∘C 12 h) to give amaterial denoted as the catalyst precursor Finally the catalystprecursor was calcined at 600∘C for 6 h to produce magneticsolid catalyst The Fe-SiO

2supported 12-tungstophosphoric

acid catalyst with 4wt of aqueous solution HPW (basedon the Fe-SiO

2weight) were prepared by incipient wetness

impregnationThe impregnated precursor was dried at 120∘Cfor overnight and calcined at 600∘C for 6 h

Finally the promoted catalyst by Cs was synthesized withCsH3PW12O40= 2wtThe salt obtained by this procedure

will be designated hereinafter as Cs119883H3minus119883

PW12O40Fe-SiO

2

where 119883 is the amount of protons per [PW12O40]3minus anion in

the salt

22 Characterization of Catalyst

221 N2Physisorption Measurements The specific surface

area total pore volume and the mean pore diameter weremeasured using a N

2adsorption-desorption isotherm at

liquid nitrogen temperature (minus196∘C) using a NOVA 2200instrument (Quantachrome USA) Prior to the adsorption-desorption measurements all the samples were degassed at110∘C in a N

2flow for 2 h to remove the moisture and other

adsorbates

222 Scanning Electron Microscopy (SEM) Themorphologyof catalyst and precursor was observed by means of an S-360Oxford Eng scanning electron microscopy

223 Fourier Transform-Infrared Spectroscopy (FT-IR)Fourier transform infrared (FT-IR) spectra of the samples

were obtained using a Bruker Vector 22 spectrometer in theregion of 400ndash4000 cmminus1

224 X-Ray Diffraction (XRD) X-ray diffraction (XRD)patterns of the catalysts were recorded on a diffractometerusing CuK

120572radiation The intensity data were collected over

a 2120579 range of 15ndash75

225 Thermal Gravimetric Analysis (TGA) and DifferentialScanning Calorimetry (DSC) The TGA and DSC were car-ried out using simultaneous thermal analyzer (PerkinElmer)under a flow of dry air with a flow rate of 50mLminminus1The temperature was raised from 20 to 700∘C using a linearprogrammer at a heating rate of 3∘Cminminus1

23 Catalytic Tests The type and quantity of methyl estersin the biodiesel samples were determined using gas chroma-tography-mass spectrometry (GC Agilent 6890N model andMass Agilent 5973N model) equipped with a flame ionizeddetector (FID) A capillary column (HP-5) with columnlength (60m) inner diameter (025mm) and 025 120583m filmthickness was used with helium as the carrier gas The tem-perature program for the biodiesel samples started at 50∘Cand ramped to 150∘Cat 10∘Cminminus1The temperaturewas heldat 150∘C for 15min and ramped to 280∘C at 5∘Cminminus1 Theholding time at the final temperature (250∘C)was 5min Alsothe injector was used from kind splitsplitless

24 Kinetic Studies The transesterification of sunflower oilwas carried out in a round bottomed flask fitted with acondenser andmagnetic stirring systemThe reaction systemwas heated to selected temperature in 50 55 and 60∘CWhenthe oil reached selected temperature methanoloil molarratio = 121 and the catalyst amount (3 wt related to oilweight) were addedwith continuous stirring (500 rpm) Aftercompletion of the reaction time (0ndash240min) the sampleconcentration is calculated according to mole fraction at anytime The results can be seen in Table 1

3 Kinetic Model

The mole fraction for the transesterification reaction wasestablished For the reaction stoichiometry requires 3Mol ofmethanol (M) and 1mol of triglyceride (TG) to give 3molof methyl ester (ME) and 1Mol of glycerol (GL) Transes-terification reaction comprises three consecutive reversiblereactions where 1mol of ME is produced in each step andmonoglycerides (MG) and diglycerides (DG) are intermedi-ate products [19]The kineticmodel used in this work is basedon the following assumptions

(1) Firstly 119896eq should be considered not to dependon methanol concentration (due to its excess) (thereaction is considered pseudo-first order [20 21])

(2) Production of intermediate species is negligible (theresult reaction is a one step)

(3) The chemical reaction occurred in the oil phase






minus119903 =

minus119889 [119879119866]

119889119905

= 119896 [119879119866] [ROH]3 (1)


119896

1015840= 119896[ROH]3

minus119903 =

minus119889 [119879119866]

119889119905

= 119896

1015840[119879119866]


(2)


119883ME = 1 minus[119879119866]

[119879119866

0]

[119879119866] = [1198791198660] [1 minus 119883ME]

119889119883ME119889119905

= 119896


1015840sdot 119905

(3)





PW12O40Fe-SiO

2


6


001020304050607

0 500 1000 1500 2000 2500 3000

Tran

smitt

ance

()


(a)

(b)

(c)


PW12O40Fe-SiO

2(a)

H3PW12O40(b) and Cs

119883H3minus119883



119883H3minus119883

PW12O40is supported





119883H3minus119883

PW12O40Fe-SiO

2catalyst




Inte

nsity

(au

)

(2 120579)20 30 40

(b)

(a)

50 60


2(a) and


70

60

50

40

30

20

10

00 100 200 300 400 500 600 700


Wt l

oss (

)

Hea

t flow

(mca

ls)

Wei

ght (

mg)

18

16

14

12

10

8

6

Temperature (∘C)


PW12O40Fe-SiO

2

precursor


2SiO4



119883H3minus119883

PW12O40Fe-

SiO2


119883H3minus119883

PW12O40Fe-SiO

2



119896 = 119860119890

minus119864119886119877119879 (4)

997904rArr ln 119896 = ln119860 minus119864

119886

119877119879

(5)







Δ119866 = minus119877119879 ln 119896eq (6)

ln 119896eq =Δ119878

119877

minus

Δ119867

119877119879

(7)



(a) (b)


002040608

112141618

0 50 100 150 200 250 300Time (min)

y = 00066x + 00836

R2 = 09908y = 00044x + 00473

R2 = 09918

y = 00027x + 00219

R2 = 09875

minusln

(1minusX

)




5 Conclusions


PW12O40Fe-SiO

2nanocatalyst was



0003 000304 000308minus91

minus92

minus93

minus94

minus95

minus96

minus97

minus98

minus99

minus10

minus101

y = minus96151x + 19763

R2 = 09998

1T

lnk


25000

25600

26200

26800

322 327 332

y = minus16397x + 79784

R2 = 09995

ΔG (JKmiddotmol)

ΔG

(JK

middotmol

)

T (K)


Acknowledgment



References














































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of






















minus119903 =

minus119889 [119879119866]

119889119905

= 119896 [119879119866] [ROH]3 (1)


119896

1015840= 119896[ROH]3

minus119903 =

minus119889 [119879119866]

119889119905

= 119896

1015840[119879119866]


(2)


119883ME = 1 minus[119879119866]

[119879119866

0]

[119879119866] = [1198791198660] [1 minus 119883ME]

119889119883ME119889119905

= 119896


1015840sdot 119905

(3)





PW12O40Fe-SiO

2


6


001020304050607

0 500 1000 1500 2000 2500 3000

Tran

smitt

ance

()


(a)

(b)

(c)


PW12O40Fe-SiO

2(a)

H3PW12O40(b) and Cs

119883H3minus119883



119883H3minus119883

PW12O40is supported





119883H3minus119883

PW12O40Fe-SiO

2catalyst




Inte

nsity

(au

)

(2 120579)20 30 40

(b)

(a)

50 60


2(a) and


70

60

50

40

30

20

10

00 100 200 300 400 500 600 700


Wt l

oss (

)

Hea

t flow

(mca

ls)

Wei

ght (

mg)

18

16

14

12

10

8

6

Temperature (∘C)


PW12O40Fe-SiO

2

precursor


2SiO4



119883H3minus119883

PW12O40Fe-

SiO2


119883H3minus119883

PW12O40Fe-SiO

2



119896 = 119860119890

minus119864119886119877119879 (4)

997904rArr ln 119896 = ln119860 minus119864

119886

119877119879

(5)







Δ119866 = minus119877119879 ln 119896eq (6)

ln 119896eq =Δ119878

119877

minus

Δ119867

119877119879

(7)



(a) (b)


002040608

112141618

0 50 100 150 200 250 300Time (min)

y = 00066x + 00836

R2 = 09908y = 00044x + 00473

R2 = 09918

y = 00027x + 00219

R2 = 09875

minusln

(1minusX

)




5 Conclusions


PW12O40Fe-SiO

2nanocatalyst was



0003 000304 000308minus91

minus92

minus93

minus94

minus95

minus96

minus97

minus98

minus99

minus10

minus101

y = minus96151x + 19763

R2 = 09998

1T

lnk


25000

25600

26200

26800

322 327 332

y = minus16397x + 79784

R2 = 09995

ΔG (JKmiddotmol)

ΔG

(JK

middotmol

)

T (K)


Acknowledgment



References














































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of


















Inte

nsity

(au

)

(2 120579)20 30 40

(b)

(a)

50 60


2(a) and


70

60

50

40

30

20

10

00 100 200 300 400 500 600 700


Wt l

oss (

)

Hea

t flow

(mca

ls)

Wei

ght (

mg)

18

16

14

12

10

8

6

Temperature (∘C)


PW12O40Fe-SiO

2

precursor


2SiO4



119883H3minus119883

PW12O40Fe-

SiO2


119883H3minus119883

PW12O40Fe-SiO

2



119896 = 119860119890

minus119864119886119877119879 (4)

997904rArr ln 119896 = ln119860 minus119864

119886

119877119879

(5)







Δ119866 = minus119877119879 ln 119896eq (6)

ln 119896eq =Δ119878

119877

minus

Δ119867

119877119879

(7)



(a) (b)


002040608

112141618

0 50 100 150 200 250 300Time (min)

y = 00066x + 00836

R2 = 09908y = 00044x + 00473

R2 = 09918

y = 00027x + 00219

R2 = 09875

minusln

(1minusX

)




5 Conclusions


PW12O40Fe-SiO

2nanocatalyst was



0003 000304 000308minus91

minus92

minus93

minus94

minus95

minus96

minus97

minus98

minus99

minus10

minus101

y = minus96151x + 19763

R2 = 09998

1T

lnk


25000

25600

26200

26800

322 327 332

y = minus16397x + 79784

R2 = 09995

ΔG (JKmiddotmol)

ΔG

(JK

middotmol

)

T (K)


Acknowledgment



References














































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of


















(a) (b)


002040608

112141618

0 50 100 150 200 250 300Time (min)

y = 00066x + 00836

R2 = 09908y = 00044x + 00473

R2 = 09918

y = 00027x + 00219

R2 = 09875

minusln

(1minusX

)




5 Conclusions


PW12O40Fe-SiO

2nanocatalyst was



0003 000304 000308minus91

minus92

minus93

minus94

minus95

minus96

minus97

minus98

minus99

minus10

minus101

y = minus96151x + 19763

R2 = 09998

1T

lnk


25000

25600

26200

26800

322 327 332

y = minus16397x + 79784

R2 = 09995

ΔG (JKmiddotmol)

ΔG

(JK

middotmol

)

T (K)


Acknowledgment



References














































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of


















References














































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of





















FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















research article kinetic study on the cs h pw o /fe-sio...

Documents