Biodiesel from Rice Bran Oil: Transesterification by Tin Compounds Sandra Einloft,* Tatiana O. Magalhães, Augusto Donato, Jeane Dullius, and Rosane Ligabue Pontifícia UniVersidade Católica do Rio Grande do Sul, Faculdade de Química/PGETEMA, P.O. Box 1429, CEP 90619-900, Porto Alegre, Brazil ReceiVed August 24, 2007. ReVised Manuscript ReceiVed October 23, 2007 The transesterification of rice bran oil with methanol has been studied in the presence of sulfuric acid (H 2 SO 4 ), tin chloride dihydrate (SnCl 2 · 2H 2 O), tin 2-ethylhexanoate (Sn(C 8 H 15 O 2 ) 2 ), dibutyl tin oxide ((C 4 H 9 ) 2 SnO), and dibutyl tin dilaurate ((C 4 H 9 ) 2 Sn(C 12 H 23 O 2 ) 2 ), known commercially as DBTDL. Through the comparative analysis among the catalysts, we observed that the complex DBTDL presented the best performance, with a yield of 68.9% in 4 h using molar ratio 400:100:1 (methanol:oil:catalyst). These results evidenced the viability of the use of metallic compounds as catalysts in the obtainment of biodiesel, an interesting alternative to basic and acid catalysis. 1. Introduction In the 1970s, the Brazilian government created a National Program to the utilization of ethanol obtained from sugar cane. Since that time, anhydrous ethanol and mixtures of it with gasoline have been used as a combustible in Otto cycle motor vehicles in Brazil. This experience is one of the most successful examples in the world in terms of biocombustibles. 1 In January 2005, the Brazilian government created a Biodiesel National Program, allowing the addition of 2% biodiesel into petroleum diesel for use in Diesel motors. The additional 2% biodiesel will be obligatory in 2008, and in 2013, the biodiesel content that must be added in the petroleum diesel will be 5% (Law no. 11097/2005). 2 These actions will contribute to reducing dependence on fossil resources as fuels. An alternative fuel for diesel engines can be obtained through transesterification reaction of vegetable oils or animal fats with an alcohol such as ethanol or methanol producing a mixture of fatty acid esters of low alkyl-chain alcohols called biodiesel. This reaction occurs in the presence of a catalyst, the most common system using acids or alkyl catalysts such as metal alkyl hydroxides or alkoxides and sulfuric acid, as show in Figure 1. 3–7 A great triglyceride source can be found worldwide for biodiesel production among rapeseed, soybean, sunflower, palm, and corn oils which are well-known and have been described in many articles. 4,6,8–10 The methanolysis of the native Brazilian oils of the Savannah and Amazon regions were described in the literature. 11 At current production levels, biodiesel requires a subsidy to compete directly with petroleum-based fuels. 3 In spite of the beneficial effects of this combustible, which is biodegradable, nontoxic, and renewable, cost is still as a major impediment for the wider biodiesel commercialization. 12 In this sense, the use of byproduct to biodiesel production can be an alternative to deal with the price problem. Rice bran a coproduct of rice milling is a low-cost feedstock option for biodiesel production, since it contains 15–25% rice bran oil which can be used as vegetable oil for the transesteri- fication reaction with alcohol to produce the methyl esters. 12,13 In the literature, we can find some examples of biodiesel obtained from rice bran oil. Among them, a study using two commercially immobilized lipases, Novozym 435 and IM 60 as catalysts for the reaction of the rice bran oil and methanol, showed that a conversion over 98% can be reached in 6 h when catalyzed by Novozym 435. 14 In another study a two-step acid- catalyzed methanolysis process was applied for the efficient conversion of rice bran oil into fatty acid methyl ester (FAME), which reached more than 98% of conversion in FAME in less than 8 h. 12 The use of a biodiesel fuel derived from the rice * Corresponding author. E-mail: einloft@pucrs.br. Tel./Fax: 55 51 33203549. (1) Holanda, H. O. Biodiesel Inclusão e a Social, Câmara dos Depu- tados; Coordenação de Publicações: Brasília-DF, 2004. (2) Biodiesel. O novo combustível do Brasil-Programa Nacional de Produção e Uso de Biodiesel. www.mme.gov.br (accessed 2006). (3) Gerpen, J. V. Fuel Process. Technol. 2005, 90, 1097–1107. (4) Ma, F.; Hanna, M. A. Bioresour. Technol. 1999, 70, 1–15. (5) Abreu, F. R.; Lima, D. G.; Hamú, E. H.; Einloft, S.; Rubim, J. C.; Suarez, P. A. Z. J. Am. Oil Chem. Soc. 2003, 80, 601–604. (6) Fukuda, H.; Kondo, A.; Noda, H. J. of Biosci. Bioeng. 2001, 92, 405–416. (7) Vicente, G.; Martínez, M.; Aracil, J. Bioresour. Technol. 2004, 92, 297–305. (8) Lang, X.; Dalai, A. K.; Bakhshi, N. N.; Reaney, M. J.; Hertz, P. B. Bioresour. Technol. 2001, 80, 53–62. (9) Barnwal, B. K.; Sharma, M. P. Renewable Sustainable Energy ReV. 2005, 9, 363–378. (10) Srivastava, A.; Prasad, R. Renewable Sustainable Energy ReV. 2000, 4, 111–133. (11) Abreu, F. R.; Lima, D. G.; Hamú, E. H.; Wolf, C.; Suarez, P. A. Z. J. Mol. Catal. A, Chem. 2004, 209, 29–33. (12) Zullaikah, S.; Lai, C.; Vali, S. R.; Ju, Y. Bioresour. Technol. 2005, 96, 1889–1996. (13) Danielski, L.; Zetzl, C.; Hense, H.; Brunner, G. J. Supercrit. Fluids 2005, 34, 133–141. (14) Lai, C.; Zullaikah, S.; Vali, S. R.; Ju, Y. J. Chem. Technol. Biotechnol. 2005, 80, 331–337. Figure 1. Transesterification reaction of triglycerides with alcohol. 10.1021/ef700510a CCC: $40.75  2008 American Chemical Society Published on Web 11/27/2007