Abstract
Compared with traditional fuels, biodiesel is a good alternative because of its advantages of biodegradability, environment friendliness, excellent lubricity, high cetane number and reduced contribution to the greenhouse effect thanks to the low levels of carbon monoxide, carbon dioxide, sulfur compounds and particulate matter emitted during the combustion process. Biodiesel is usually produced by transesterification reaction of vegetable oils with methanol, using homogeneous catalysts such us NaOH, KOH and their alkoxides. However, homogeneous catalysts require a significant amount of water to transfer the dissolved catalysts from biodiesel. Further, this catalysts form saponified products which can lower the yield of methyl esters. Instead, heterogeneous catalysts are environmentally benign, much easier to separate from biodiesel and they can be reused and regenerated, giving a higher activity and selectivity.
In this paper, it was studied the transesterification of sunflower oil to biodiesel using two types of solid calcium oxide CaO as heterogeneous catalyst, due to its low cost and high activity: solid calcium oxide powder kept at room atmosphere and solid calcium oxide freshly synthesized from CaCO3 by calcination. These catalysts were analyzed with XRD spectroscopy, in order to establish the composition and with optical microscopy to estimate the form and the dimension of catalysts particles. Also, biodiesel samples obtained by transesterification with CaO were compared with biodiesel synthesized by traditional catalyst NaOH by IR analyze and physical chemical characteristics: saponification, acid, iodine and peroxide values, density and viscosity.
Keywords: Biodiesel, Transesterification, Heterogeneous catalysts, Calcium oxide, Sunflower oil