Characterization of Blend Properties of Castor Biodiesel andBioethanolNívea de Lima da Silva,* Carlos M. García Santander, Sandra M. Gomez Rueda, Maria R. Wolf Maciel,and Rubens M. Filho

School of Chemical Engineering, State University of Campinas (UNICAMP), Campinas, Brazil

ABSTRACT: Some important properties of biodiesel such as viscosity, melting point, thermal stability, and cetane index can bedirectly related to the chemical composition of the biomass source used. However, the viscosity of castor oil ethyl ester (COEE)is about four times greater than the biodiesel viscosity specification, and this fact restricts the uses of this biofuel. The main goalof this work is to investigate the physical−chemical properties of COEE in ethanol blends and present an option to decrease thecastor oil biodiesel viscosity specification. COEE viscosity is 14.413 mm2/s. The results show an evident decrease in biodieselviscosity with the addition of ethanol. Samples with 30, 40, and 50 vol % of ethanol present the following viscosities 5.316, 4.044,and 3.136 mm2/s, respectively. These results are in agreement with Brazilian National Agency of Petroleum, Natural gas andBiodiesel (ANP), and European (EN 14214) specifications. Three correlations that describe the decrease in viscosity and densitywith ethanol concentration, and the variation of viscosity with the density in COEE ethanol blends were obtained. The behaviorof COEE ethanol blends with diesel also were analyzed. The increase in solubility of ethanol in commercial diesel was verifiedbecause COEE acts as a cosolvent in an ethanol−diesel mixture.

1. INTRODUCTION

Biodiesel is derived from different lipid sources such as refinedor used vegetable oils and animal fats. It can be used as asubstitute for conventional petroleum fuel in diesel engineswithout modifications. The use of the fatty acid esters as a fueldecreases the particulate material and greenhouse gasemissions. Furthermore, biodiesel fuel can be used in its purestate or blended with conventional diesel fuel.1,2

The use of vegetable oils as alternative fuel for diesel engineshas been studied by many researchers. It has been notedhowever, that the direct use of vegetable oils in engines islimited by some physical properties including its high viscosity,low volatility, and the fact that it is polyunsaturated. As a result,the use of oil without chemical modification can cause damageto engines and create environmental problems because of itsincomplete combustion. In recent years, global warming andenvironmental pollution have become major issues. The use offuels coming from biomass such as biodiesel and bioethanol canhelp solve such matters because of the renewable features ofthese energy sources.3,4

Density and viscosity are two important properties that areuseful for selecting fuels. The effects of temperature and volumefraction of biodiesel and diesel on the density and kinematicviscosity of blends were investigated by Moradi et al. Theseauthors concluded that when reducing temperature andincreasing the volume fraction of biodiesel, density andkinematic viscosity are increased.5

Castor oil (Ricinus communis L., higuerilla, mamona or palmchristi) is one of the most important possible feedstocks amongseveral options currently available in Brazil for biodieselproduction. This vegetable oil is composed almost entirely(90 wt %) of triglycerides of ricinoleic acid, and this fatty acidpresents a hydroxyl group at C-12. The hydroxyl group givescastor oil and its derivatives complete solubility in alcohols at

room temperature. The ricinoleic acid is the main componentof castor oil with numerous applications such as the basis in themanufacture of cosmetics and many pharmaceutical drugs.6

This vegetable oil is not used in the food chain (nonedibleoil) and long storage times are unproblematic under airtightconditions.7 Regarding the fuel-related properties, castor oil hasa high cetane number and calorific value, a low phosphoruscontent, and low carbon residues. A disadvantage of castor oil isits significantly higher viscosity at temperatures under 50 °C,and possibly also its higher compressibility compared to othervegetable oils. This may cause problems at extraction andinjection.8 A further disadvantage is its hygroscopicity, causinghigh water content and thereby possible algae growth, filtration,and corrosion problems.9

Published literature about COEE blends is scarce.Albuquerque et al. analyzed the viscosities of pure and mixturesof soybean oil, castor oil, cotton oil, and canola oil biodiesels.10

They found that mixtures of castor oil biodiesel with soybeanand cotton biodiesel oils up to 20 vol % of castor biodieselsatisfy the specification of these blends within European limits.For canola and castor blends, none of the mixtures comply withthe specification, even at low contents of castor biodiesel oil.10

Thomas et al. studied the decrease of castor oil biodieselviscosity with the addition of ten chemical additives, blendswith cotton esters and sunflower esters.11 According to Berrios,the viscosity of biodiesel and biodiesel blends with dieselincrease during storage due the formation of acids and oxidized

Special Issue: NASCRE 3

Received: March 1, 2013Revised: June 24, 2013Accepted: June 25, 2013

Article

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© XXXX American Chemical Society A dx.doi.org/10.1021/ie400680t | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

polymeric compounds. They state that blends containing 40 wt% of castor oil biodiesel fulfill ANP specifications.12

Ethanol (bioethanol) from sugar cane is an alternative tomethanol in biodiesel production because it allows for theproduction of an entirely renewable fuel.13 The use of ethanolin diesel began in the 1970s and has led to a reduction in levelsof pollution with a reduction in smoke opacity and particulatematerial in exhaust fumes. However, the blending proportion ofethanol is limited because of its low ignitability, reduced heatingvalue, and limited miscibility in petroleum diesel at lowtemperatures.14 According to Park et al., the addition ofbioethanol fuel improved the fuel atomization performance ofbiodiesel−bioethanol blended fuels due to a more activebreakup process influenced by the low kinematic viscosity andincreased fuel evaporation of bioethanol fuel.15

This work presents a study of castor oil ethyl ester (COEE)blends with bioethanol in order to adjust the COEE viscosity.The influence of the ethanol content in COEE viscosity anddensity is presented. Three correlations that describe thedecrease in viscosity and density with ethanol concentrationand variation of the viscosity with the density in COEE ethanolblends were obtained. Finally, the COEE ethanol blend wasadded to commercial diesel in order to verify the stability of thismixture.

2. EXPERIMENTAL PROCEDURE

2.1. Materials. The experiments were carried out withcommercial castor oil obtained from Aboissa (Brazil). Sodiumhydroxide (Synth) and anhydrous ethanol (Synth) were usedto produce the biodiesel and blends. The anhydrous sodiumsulfate (Synth) was used in the biodiesel purification step. Allthe standards were supplied by Sigma-Aldrich (St. Louis, Mo).The polytetrafluorethylene filter (PTFE filter) supplied byMillipore (USA), HPLC-grade THF (tetrahydrofuran) fromB&J/ACS (USA).2.2. Experimental Conditions and Procedures. The

transesterification reaction was carried out in a 1 L batch stirredtank reactor (BSTR) equipped with a reflux condenser, amechanical stirrer, and a stopper to remove samples.2.3. Method of analysis. 2.3.1. Chromatographic Anal-

ysis. The fatty acid compositions of castor oil were obtainedusing the following methodology: the ethyl esters wereobtained according to the item 2.2, then 0.1 g of ethyl esterswas diluted in 10 mL of n-heptane, and the samples werefiltered using a PTFE filter and analyzed by gas chromatog-raphy (GC). The GC was equipped with a flame ionizationdetector (FID) and with a DB 23 column. Injector and detectortemperatures were set at 250 and 300 °C, respectively. Thecarrier gas used was helium at 46 mL/min. Air and hydrogenflow rates were 334 and 34 mL/min, respectively. Oventemperature programming was as follows: starting at 50 °C for2 min; from 50 to 180 °C at 10 °C/min; 180 °C was held for 5min; from 180 to 240 °C at 5 °C/min. Identification ofdifferent FAEEs were based on a reference standard (Sigma-Aldrich).The transesterification reaction composition was determined

by high-performance size-exclusion chromatography (HPSEC)supplied by Waters (U.S.). The HPSEC was equipped with twocolumns Styragel HR 0.5 and HR 2 which were connected inseries and with a differential refractometer detector model2410. The mobile phase was tetrahydrofuran (HPLC-grade,Tedia).

2.3.2. Free Fatty Acid Content. The free fatty acid contentwas determined according to the AOCS official method Ca 5a-40 as oleic acid.

2.3.3. Determination of Viscosity and Density. Theseproperties were measured at 40 °C (313 K) according to theASTM D-445. The viscometer works according to a newpatented (EP 0 926 481 A2) measuring principle. Themeasuring cell is filled with 3 mL of the sample, and thekinematic viscosity and density values are obtained.

2.3.4. Determination of Enthalpy and Heat Capacities.The samples weighed 15 mg of COEE and blends. First, thesamples were weighed and placed in a pan (Aluminum of 40 μL) inside the furnace. Samples were analyzed with a heatingrate of 20 °C/min, using as inert gas nitrogen on a flow of 50mL/min, according to ASTM designation E1269-01. Adynamic method of heating with temperatures of 40−250 °Cwas used. This property was measured in the following samples:diesel (D), 10 vol % of sample 15 plus diesel (D + 10 vol % ofS15) and 10 vol % of sample 16 plus diesel (D + 10 vol % ofS16). The heat capacity is a quantitative measurement ofenergy as function of temperature.

3. RESULTSThe castor oil contained 1.2% of free fatty acid (FFA). Table 1depicts the fatty acid composition of castor oil determined byGC.

3.1. Viscosity and Density. Table 2 presents the blendviscosities and densities. The COEE presents higher viscositythan the diesel specification (sample 1); according to theBrazilian National Agency of Petroleum, Natural gas and

Table 1. Fatty Acid Compositiona

fatty acid name structure molar mass composition (wt %)

palmitic C16H32O2 256.43 1.6stearic C18H36O2 284.48 0.9oleic C18H34O2 282.47 3.0ricinoleic C18H34O3 298.46 89.5linoleic C18H32O2 280.45 3.7linolenic C18H30O2 278.43 0.4arachidic C20H40O2 312.53 0.3behenic C22H44O2 340.58 0.6

aDa Silva et al.13

Table 2. COEE Ethanol Blend Viscosity and Density

sample ethanol (vol %) viscosity (mm2/s) density (kg/m3)

1 0 14.413 9022 1 13.788 9003 2 13.235 8994 3 12.836 8986 5 11.890 8968 6 11.299 8949 7 10.860 89310 8 10.591 89211 9 10.234 89112 10 9.966 89113 20 7.290 87914 30 5.316 86615 40 4.044 85316 50 3.136 841

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Biodiesel (ANP) norms the biodiesel viscosity must be from 3.0to 6.0 mm2/s. The castor oil biodiesel viscosity was about fourtimes higher than the diesel values. According to Cvengros etal., the presence of the hydroxyl group in ricinoleic esters isreflected in the COEE properties.16 High viscosity leads topoorer atomization of the fuel spray and less accurate operationof the fuel injectors.17 Therefore the COEE ethanol blend is away to decrease viscosity. In order to promote COEE viscosityspecification 15 blends of COEE ethanol were investigated. Theresults show an evident decrease in biodiesel viscosity with theaddition of ethanol. ANP specification of viscosity and densityare from 3.0 to 6.0 mm2/s and from 850 to 900 kg/m3. Thesamples 14, 15, and 16 present viscosity according to ANPspecifications.Figures 1 and 2 show the slope of viscosity and density

decrease as the amount of ethanol increases. The decrease in

viscosity is according to a exponential function (eq 1), where vis the viscosity (mm2/s), y0 and A are coefficients, and X is thequantity of ethanol (vol %).

ν = + −⎜ ⎟⎛⎝

⎞⎠y A

Xt

exp0 (1)

The density delay follows a linear behavior, eq 2, where D isthe density (kg/m3), A and B are coefficients, and X is thequantity of ethanol (vol %).

= +D A BX1 (2)

These correlations are important to determine the quantityof ethanol necessary to meet ANP specifications and the slopesshows the tendency or behavior of the blends. The variation inviscosity with the density of COEE ethanol blends is presentedin Figure 3. Equation 3 describes the relationship between the

kinematic viscosity and density and using this correlation it ispossible to predict the viscosity of the mixture by the densityobtained in eq 2.

ν = +⎛⎝⎜

⎞⎠⎟y A

Dt

exp1 21 (3)

Where v is viscosity (mm2/s), y1, A2, and t1 are coefficients andD is density (kg/m3).

3.2. Heat Capacity. The heat capacity of COEE ethanolblends is presented in Figure 4. The slope of diesel and theCOEE ethanol blends show similar behavior and up to 200 °Cthe graph shows the stability of each sample. This is indicativeof the influence of COEE in the mixture because the normalboiling point of ethanol is 78 °C, but the COEE ethanol blendin diesel can be heated up to 200 °C without degradation. Thediesel sample presents a higher increase in heat capacity withtemperature because less volatile fuels have higher heatingvalues (energy content).

3.3. Castor Oil Biodiesel Properties. Table 3 shows thecastor oil ethyl esters properties. The results of the sulfurcontent, iodine index, copper corrosion, water, sediments, flashpoint, oxidative stability, and cetane index conform with theASTM and EN norms. The oxidative stability was about 7 timeshigher than the Brazilian and Europe specification; therefore,the castor oil ethyl ester is not sensitive to oxidativedegradation.16,18 The oxidation of COEE ethanol blend withdiesel is a function of the composition of the mixture, and it isaccelerated by the presence of oxygen, light, and temperature;however, its speed is primarily dependent on its composition, asobserved by D’Ornellas for ethanol gasoline blends.19

4. CONCLUSIONThe use of ethanol in the blends (at 30, 40, and 50 vol %)enabled the viscosity of COEE to meet the ANP standards. TheCOEE and ethanol are completely soluble therefore theseesters could act as an antioxidant. The mixture of ethanol and

Figure 1. COEE viscosity decrease with bioethanol content at 40 °C.

Figure 2. Castor oil biodiesel density decrease with bioethanol contentat 40 °C.

Figure 3. Variation in viscosity with the density in COEE ethanolblends.

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diesel was not completely soluble, and this promotes phaseseparation at low temperatures. However, in this case, theCOEE could act as a cosolvent because it is soluble in alcoholsand diesel. Consequently, the mixtures with COEE presentstability with temperature increases or decreases.The use of the correlation obtained in this study enables the

prediction of the COEE ethanol blend viscosity and densitywith ethanol content. This work presents an alternative todecrease castor oil biodiesel viscosity with the addition ofalcohols. It is a promising possibility because the addition ofoxygenated components in diesel, such as alcohols and esters,increase complete diesel combustion, reducing the carbonmonoxide and particulate material emissions. On the otherhand, there is a decrease in the cost of the COEE ethanol blendbecause the price of Brazilian ethanol is about 1/2 that ofbiodiesel.

■ AUTHOR INFORMATIONCorresponding Author*Phone: 551935213971. E-mail: niveals@feq.unicamp.br.

NotesThe authors declare no competing financial interest.

■ REFERENCES(1) Da Silva, N. L.; Garnica, J. A. G.; Batistella, C. B.; Wolf Maciel, M.R.; Maciel Filho, R. Use of experimental design to investigate biodieselproduction by multiple-stage ultra shear reactor. Bioresour. Technol.2011, 102, 2672−2677.(2) Yusaf, N. N. A. N.; Kamarudin, S. K.; Yaakub, Z. Overview on thecurrent trends in biodiesel production. Energy Convers. Management2011, 52 (7), 2741−2751.(3) García, M.; Gonzalo, A.; Sanchez, J. L.; Arauzo, J.; Pena, J. A.Prediction of normalized biodiesel properties by simulation of multiplefeedstock blends. Bioresour. Technol. 2010, 101, 4431−4439.(4) Shang, Q.; Jiang, W.; Lu, H.; Liang, B. Properties of Tung oilbiodiesel and its blends with 0# diesel. Bioresour. Technol. 2010, 101,826−828.(5) Moradi, G. R.; Karami, B.; Mohadesi, M. Densities and KinematicViscosities in Biodiesel−Diesel Blends at Various Temperatures. J.Chem. Eng. Data 2013, 58, 99−105.(6) Severino, L. S.; Auld, D. L.; Baldanzi, M.; Candido, J. D.; Chen,G.; Crosby, W.; Tan, D.; He, X.; Lakshmamma, P.; Lavanya, C.;Machado, O. L. T.; Mielke, T.; Milani, M.; Miller, T. D.; Morris, J. B.;Morse, S. A.; Navas, A. A.; Soares, D. J.; atti, V. S.; Wang, M. L.;Zanotto, M. D.; Zieler, H. A Review on the Challenges for IncreasedProduction of Castor. Agron. J. 2012, 104, 853−880.(7) Boilley, D. S. Composition of Castor Oil by Optical Activity. J.Am. Oil Chem. Soc. 1953, 30, 396−398.(8) Labalette, F. A.; Estraganat, A.; Messean, A. Development ofcastor bean production in France. In Progress in new crops; Janick, J,Ed.; Alexandria: ASHS Press, 1996; pp 340−342.(9) Kitani, O. CIGR handbook of agricultural engineering; ASAE: St.Joseph, MI, 1999.(10) Albuquerque, M. C. G.; Machado, Y. L.; Torresa, A. E. B.;Azevedo, D. C. S.; Cavalcante, C. L., Jr.; Firmiano, L. R.; Parente, E. J.S., Jr. Properties of biodiesel oils formulated using different biomasssources and their blends. Renewable Energy 2008, 34 (3), 857−859.(11) Thomas, T. P.; Birney, D. M.; Auld, D. L. Viscosity reduction ofcastor oil esters by the addition of diesel, safflower oil esters andadditives. Ind. Crops Prod. 2012, 37, 267−270.(12) Berrios, M.; Martín, M. A. M.; Chica, A. F.; Martín, A. A.Storage effect in the quality of different methyl esters and blends withdiesel. Fuel 2012, 91, 119−125.

Figure 4. Cp of diesel and diesel blends.

Table 3. Castor Oil Ethyl Ester Propertiesa

properties method limitsethyl esters ofcastor oil

iodine index (g/100 g) EN 14110 120;max

83.2 ± 0.2

copper corrosion ASTM D130 1 1water and sediments (vol %) ASTM D2709 0.05;

max0.05 (less than)

lower heating value (mJ/kg) ASTM D240-02(07)

35.25

sulfated ash (wt %) ASTM D874-00

0.02;max

0.01 (less than)

sulfur cotent (mg/kg) ASTM D5453-06

50; max 2

mono, di, triglyceridescontent (wt %)

EN 14105-03 0.5 (less than)

oxidation stability (h) EN 14112-03 6; max 46aDa Silva et al.13

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(13) Da Silva, N. L.; Batistella, C. B.; Maciel Filho, R.; Wolf Maciel,M. R. Biodiesel production from castor oil: Optimization of alkalineethanolysis. Energy Fuel 2009, 23, 5636−5642.(14) Lapuerta, M.; Armas, O.; Garcia-Contreras, R. Effect of Ethanolon blending Stability and Diesel Engine Emissions. Energy Fuel 2009,23, 4343−4354.(15) Park, S. H.; Suh, H. K.; Lee, C. S. Effect of Bioethanol-BiodieselBlending Ratio on Fuel Spray Behavior and Atomization Character-istics. Energy Fuels 2009, 23, 4092−4098.(16) Cvengros, J.; Paligova, J.; Cvengrosova, Z. Properties of alkylesters base on castor oil. Eur. J. Lipid Sci.Technol 2006, 108, 629−635.(17) Dermirbas, A. Blending biodiesel with diesel introduces oxygencompression ratio and ignition timing. Fuel 2007, 87, 1743−1748.(18) Berman, P.; Nizri, S.; Wiesman, Z. Castor oil biodiesel and itsblends as alternative fuel. Biomass Bioenergy 2011, 35, 2861−2866.(19) D’Orenellas, C. V. The Effect of Ethanol on Gasoline OxidationStability. SAE International Fall Fuels & Lubricants Meeting &Exhibition, San Antonio, TX, Sept 24, 2001; Session: SI EnginePerformance & Fuel Effects (Part A&B), Document Number: 2001-01-3582.

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