Organotin(IV) carboxylates as an effective catalyst for the conversion of corn oil into biodiesel Muhammad Sirajuddin a, b, * , Muhammad Tariq c , Saqib Ali a, * a Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan b Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad 22060, Pakistan c Department of Chemistry, Bahauddin Zakariya University, Multan 60000, Pakistan article info Article history: Received 11 September 2014 Received in revised form 13 December 2014 Accepted 16 December 2014 Available online 24 December 2014 Keywords: Organotin(IV) carboxylate Transesterification Corn oil Biodiesel NMR abstract Biodiesel fuel has shown great promise as an alternative to petro-diesel fuel. Biodiesel production is widely conducted through transesterification reaction, catalyzed by homogeneous catalysts or hetero- geneous catalysts. Fourteen new organotin(IV) carboxylate complexes were preliminary screened for their catalytic activity in transesterification. The transesterification reaction, which is a major path to produce biodiesel, occurs between the triglyceride vegetable oils with alcohols to form esters (biodiesel) and glycerol. The present investigation involves the production of environmental-friendly heterogeneous catalyst, organotin(IV) carboxylates, for biodiesel production from corn oil. 83% Conversion of corn oil into biodiesel was obtained in the presence of the synthesized catalysts. Therefore, the newly synthe- sized organotin(IV) carboxylate complexes can be used as one of the best catalysts in future for the biodiesel synthesis. © 2014 Elsevier B.V. All rights reserved. Introduction Energy is the prime mover for socio-economic development. The World's economic growth is affected by climatic change, fuel price hike, and the gradual depletion of fossil fuel reserves. Therefore, to increase energy security for economic development, the need to search for an alternative source of energy such as biodiesel is necessary [1]. Finding an alternative fuel has attracted considerable attraction in recent years due to limitation of traditional fossil re- sources and increasing of crude oil prices as well as concern over greenhouse gas emissions [2]. Biodiesel is nothing but fatty acid alkyl esters derived from natural vegetable oils and animal fats by a transesterification process. The demand for biodiesel as an alter- native and potentially sustainably renewable fuel for diesel engines is increasing steadily due to economic and environmental issues. These include increases in the crude oil price, as well as the decreasing but limited supplies of the non-renewable conventional diesel. Before the 1990s, the relatively high price of biodiesel that was mainly produced from refined vegetable oils, was the most severe barrier to its development and its use could not economically compete against conventional diesel [3]. However, due to the rela- tively high price of conventional diesel at present, biodiesel pro- duced from both refined and spent vegetable or animal oils/fats has begun to become competitive [4]. On the other hand, the global warming issue makes biodiesel attractive as it has a closed carbon cycle and can effectively reduce the CO 2 emission burden from transportation and industry. For instance, biodiesel decreases the net CO 2 emission by 78% compared with conventional diesel [5,6]. Furthermore, biodiesel emits a lower level of CO, SO x and unburned hydrocarbons after combustion than that for conventional diesel [6]. Finally, biodiesel has the potential, to be a sustainable renewable resource. Therefore, research on biodiesel production technologies has received continuous attention globally [7]. Biodiesel has been produced by transesterification reaction of vegetable oil with alcohol using acid or base catalysts as shown in Fig. 1(a). In the presence of water, the triglyceride can be partially hydrolyzed to fatty acids and diglyceride under suitable conditions (catalyzed or supercritical condition), as shown in Fig. 1(b). Those fatty acids, including the free fatty acids (FFA) present in the feedstock, also convert to the desired product (biodiesel) through * Corresponding authors. Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan. Tel.: þ92 51 90642130; fax: þ92 51 90642241. E-mail addresses: m.siraj09@yahoo.com (M. Sirajuddin), drsa54@yahoo.com (S. Ali). Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem http://dx.doi.org/10.1016/j.jorganchem.2014.12.019 0022-328X/© 2014 Elsevier B.V. All rights reserved. Journal of Organometallic Chemistry 779 (2015) 30e38