Synthesis and Determination of Biodiesel: An Experiment for HighSchool Chemistry LaboratoryJun Yang,†,‡ Chunli Xu,*,†,‡ Baoxin Li,‡,§ Guijia Ren,†,‡ and Lu Wang†,‡

†Key Laboratory of Applied Surface and Colloid Chemistry, Shaanxi Normal University, Ministry of Education, Xi’an 710062, PRChina‡School of Chemistry and Chemical Engineering, Shaanxi Normal University, Chang’an South Road 199, Xi’an 710062, PR China§Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, Shaanxi Normal University, Xi’an, 710062, PR China

*S Supporting Information

ABSTRACT: Biodiesel has gained attention in recent years as a renewable andenvironmentally friendly fuel source. A laboratory experiment designed for high schoolstudents is described to study biodiesel production. Under optimum conditions, the time ofrunning the reaction of biodiesel synthesis was less than a half-hour. Moreover, based on thedifference in density and solubility of reactants and products in the transesterification, onevisualizing method of detection of biodiesel product was suggested. The resultsdemonstrated that the visualizing method was simple, quick, and effective in determiningwhether biodiesel was produced. This proposed experiment is typically completed in lessthan two one-hour laboratory periods, which makes it suitable for a high school chemistrylaboratory.

KEYWORDS: High School/Introductory Chemistry, Organic Chemistry, Laboratory Instruction, Hands-On Learning/Manipulatives,Inquiry-Based/Discovery Learning, Biotechnology, Catalysis, Student-Centered Learning, Synthesis

Transesterification is an important chemical reaction foundin high school textbooks.1 It is the process of exchanging

the organic group R″ of an ester with the organic group R′ ofan alcohol (Scheme 1). These reactions are often catalyzed by

the addition of an acid or base catalyst. Catalysis, esters,alcohols, and edible oils are also important topics found in highschool textbooks.2 A simple and interesting experiment ishelpful for high school students to understand this reaction.Biodiesel is a fashionable topic nowadays because it is

environmentally friendly and is made from renewableresources.3 Biodiesel is a term applied to a fuel derived fromthe transesterification of vegetable oils or animal fats. In theproduction of biodiesel, the triglycerides in the fats and oilsreact with methanol to make glycerine and methyl esters(biodiesel) in the presence of a catalyst (Scheme 2). Wedescribe a biodiesel synthesis that is suitable for high schoolstudents to learn about transesterification, catalysis, esters,alcohols and edible oil.There have been several excellent experiments about

biodiesel published for undergraduate students in recent yearsthat include new and used oil and determination of properties,

such as combustion and viscosity of biodiesel.4−9 However, tothe best of our knowledge, there is not a laboratory experimentabout biodiesel for high school students. In those publishedexperiments, instruments, such as gas chromatography,7 IRspectroscopy,6 thin-layer chromatography,7 and 1H NMRspectroscopy,5 were used to determine the yield of biodiesel.Though these methods are accurate, these instruments areexpensive and are typically not available to high schoolstudents. Furthermore, the fundamentals of these instrumentsare also unknown to high school students. In addition, thesemethods of detection are time-consuming. Therefore, thesemethods of instrumental analysis are not suitable for a highschool chemistry laboratory. A simple and quick chemicalexperiment is suitable for the education of high schoolstudents.10,11

Published: September 11, 2013

Scheme 1. Transesterification between Alcohol and Ester

Scheme 2. Production of Biodiesel throughTransesterification

Laboratory Experiment

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In this work, a biodiesel synthesis utilizing transesterificationwas designed for the high school chemistry laboratory. In thepresence of an active catalyst NaOH, the reaction for biodieselsynthesis could be completed in 30 min. Referring to thereaction shown in Scheme 2, the density of reactant methanol(0.79 g cm−3) was lower than that of reactant vegetable oil(0.919−0.925 g cm−3), whereas the density of byproductglycerol (1.261 g cm−3) was higher than that of productbiodiesel (0.85−0.90 g cm−3). Based on the difference indensity and solubility of reactants and products in thetransesterification, a visualizing method of analysis of thereaction product was used. As shown in Figure 1, methanol

floated on triglyceride before reaction, whereas the byproductglycerine was below the layer of product biodiesel afterreaction. Through the difference in appearance of the reactionsystem before and after reaction, one can determine whetherbiodiesel was produced. This method is simple and quick, and itis suitable for high school chemistry students.

■ EXPERIMENT

Chemicals

Vegetable oils are available in supermarkets: sesame oil,soybean oil, canola oil, peanut oil, olive oil, and so forth.Methanol and NaOH used were of analytical grade. All reagentswere used without further purification.Procedure

The catalytic transesterification reaction was carried out undervigorous magnetic stirring in a round-bottomed flask equippedwith a reflux condenser. The reaction was heated by anelectromagnetic heater. Typical reactions were performed with11.76 mL of vegetable oil and 2.78 mL of methanol (methanolto vegetable oil molar ratio 6:1) using 1 wt % (catalyst to oilweight ratio) of NaOH catalyst at methanol reflux temperature(65 °C) for 10 min. After cooling, the solution was transferredto a transparent vial. After standing for 5 min, the interfacebetween biodiesel layer and glycerol layer was clearly observed.As shown in Figure 1, formation of biodiesel was analyzed by avisualizing method. The analysis of product was completedwithin 20 min.To validate its viability, the visualizing method was checked

by 1H NMR spectroscopy. 1H NMR spectroscopy provided theaccurate yield. The NMR spectra of vegetable oil and biodieselare shown in Figure S4 (see the Supporting Information). Theinstructors obtained the NMR of the products to confirm thepresence of the biodiesel and glycerol. They did not share the

spectra with the student to show the differences between thetwo layers. For this instrumental method, the reaction productswere analyzed using the following procedure: The biodieselsamples were separated from glycerol by centrifugation, withthe separation of glycerol being achieved because it wasinsoluble in the esters and had a much higher density. Afterremoval of methanol residue in vacuo, the product wasdissolved in chloroform-d and the methyl ester could bedetermined quantitatively from the NMR spectra using themethod described by Gelbard et al.12

Students worked in groups. The experiment could be dividedinto two 50 min sessions. Students run reactions (with andwithout catalyst) in the first session. They repeated theprocedure to investigate different oils and the effect of thecatalyst in the second session.

■ HAZARDSThe vegetable oils purchased in markets are edible. Methanol isflammable and poisonous so it must be handled with care.Anhydrous sodium hydroxide is irritant and caustic. In thiswork, 1H NMR spectroscopy was used to evaluate theproposed visualizing method, but not incorporated into theexperiment for high school students. If evaluation of theproduct by 1H NMR spectroscopy is incorporated, chloroform-d is needed. Chloroform-d is poisonous and must by handledwith care.

■ RESULTS AND DISCUSSIONThe yield of biodiesel was affected by reaction variables, such asthe methanol/oil ratio, catalyst amount, or reaction time.13

Under the reaction conditions of catalyst (0.3−1.0 wt %) andmethanol to vegetable oil molar ratio (6:1), a clear interfacebetween biodiesel and glycerol was observed at 10 min ofrunning time (Figure 2). This indicated that reaction time oftransesterification could be reduced to 10 min.

The type of vegetable oil was also studied. The vegetable oilstested were sesame oil, canola oil, and soybean oil. Thephotographs show that biodiesel was produced in each case(Figure 3). One phenomenon observed was the color of theglycerol layer. Pure glycerol is colorless and transparent;however, the glycerol layer in the biodiesel system was coloredand not transparent. The glycerol layer contained, besides themain components of glycerol, minor amounts of methanolresidue, NaOH residue, and sodium salt of fatty acid (soap).The sodium salt of fatty acid could accumulate colorfulcomponents of oil, which resulted in the color of glycerollayer.14

Figure 1. Photograph of transesterifaction of vegetable oil andmethanol for biodiesel synthesis: (A) before reaction and (B) afterreaction.

Figure 2. Effect of the catalyst amount (from left to right: 0, 0.3, 0.5,0.6, 0.8, 1.0 wt %).

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The benefits of the proposed experiment to students are asfollows:

• To train the students in experimental techniques relatingto reflux. Biodiesel was synthesized by using a refluxapparatus.

• To develop the students’ ability of applying chemicalknowledge of transesterification.

• To stimulate the students’ interest in chemical research.Through the proposed experiment, students learn amethod to synthesize biodiesel.

• To increase the students’ understanding about catalysis.• To teach students the concept of density. The proposed

experiment illustrates the visual density differences in thestarting materials and products.

• To increase the understanding of students on the topicsof esters, alcohols, and edible oils. In this experiment,alcohol and edible oil (ester) are used as both reactantsand products.

■ CONCLUSIONSA simple and quick chemical experiment of biodiesel synthesisfor high school students is described. This experiment is helpfulfor high school students to understand transesterification,catalysis, esters, alcohols, and biodiesel. This experiment wastypically completed in less than two hours: a half-hour forpreparation, a half-hour for running the reaction of biodieselsynthesis, and 20 min for analyzing the product. Thisexperiment is suitable for a high school chemistry laboratory.

■ ASSOCIATED CONTENT*S Supporting Information

Student handout; tables of the equipment and chemicalsneeded; procedure and tips for the experiment; answers toprelab questions. This material is available via the Internet athttp://pubs.acs.org.

■ AUTHOR INFORMATIONCorresponding Author

*E-mail: xuchunli@snnu.edu.cn.Notes

The authors declare no competing financial interest.

■ ACKNOWLEDGMENTSWe thank students (Hongyu Liang, Yan Guo, Lan Ma, ShufengJi, Yahong Li, Xinrui Qin, Jiaoyan Xiang, Liming Tan, XueqinZhao) for testing the experiment.

■ REFERENCES(1) Chemistry textbook for high school (II, a required course); People’sEducation Press: Beijing, 2007; pp 73−76.(2) Chemistry textbook for high school (V, an elective course); People’sEducation Press: Beijing, 2007; pp 45−96.(3) Leung, D. Y. C.; Wu, X.; Leung, M. K. H. A review on biodieselproduction using catalyzed transesterification. Appl. Energy 2010, 87,1083−1095.(4) Bucholtz, E. C. Biodiesel synthesis and evaluation: An organicchemistry experiment. J. Chem. Educ. 2007, 84, 296−298.(5) Bladt, D.; Murray, S.; Gitch, B.; Trout, H.; Liberko, C. Acid-catalyzed preparation of biodiesel from waste vegetable oil: Anexperiment for the undergraduate organic chemistry laboratory. J.Chem. Educ. 2011, 88, 201−203.(6) Ault, A. P.; Pomeroy, R. Quantitative investigations of biodieselfuel using infrared spectroscopy: An instrumental analysis experimentfor undergraduate chemistry students. J. Chem. Educ. 2012, 89, 243−247.(7) Behnia, M. S.; Emerson, D. W.; Steinberg, S. M.; Alwis, R. M.;Duenas, J. A.; Serafino, J. O. A simple, safe method for preparation ofbiodiesel. J. Chem. Educ. 2011, 88, 1290−1292.(8) Akers, S. M.; Conkle, J. L.; Thomas, S. N.; Rider, K. B.Determination of the heat of combustion of biodiesel using bombcalorimetry. A multidisciplinary undergraduate chemistry experiment.J. Chem. Educ. 2006, 83, 260−262.(9) Clarke, N. R.; Casey, J. P.; Brown, E. D.; Oneyma, E.; Donaghy,K. J. Preparation and viscosity of biodiesel from new and usedvegetable oil. An inquiry-based environmental chemistry laboratory. J.Chem. Educ. 2006, 83, 257−259.(10) Cai, J.; Chen, L. An improved method for catalytic oxidation ofethanol. Chin. Educ. Chem. 2009, 10−12.(11) Song, Z.; Chen, C. An improved method for catalytic oxidationof ethanol. Chin. J. Chem. Educ. 2011, 72−74.(12) Gelbard, G.; Bres, O.; Vargas, R.; Vielfaure, F.; Schuchardt, U.

1H nuclear magnetic resonance determination of the yield of thetransesterification of rapeseed oil with methanol. J. Am. Oil Chem. Soc.1995, 72, 1239−1241.(13) Ma, F. R.; Hanna, M. A. Biodiesel production: a review.Bioresour. Technol. 1999, 70, 1−15.(14) Li, C.; Jiang, L.; Cheng, S. Biodiesel-Green Energy; ChemicalIndustry Press: Beijing, 2007; p 73.

Figure 3. Photographs of reaction system using different vegetable oilsas reactants: (A) sesame oil, (B) canola oil, and (C) soybean oil (left,before reaction; right, after reaction).

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