Estudo do poder catalítico de óxidos a base de resíduos de carapaças de sururu na síntese de biodiesel etílico e metílico a partir do óleo de fritura

Abstract

The search for alternative solutions to oil consumption has been growing, due to the alarming acceleration of global warming. As an alternative, the use of green chemistry appears in order to revert this aggressive process to the environment, and biofuels appear as allies. Among biofuels, biodiesel is shown as an alternative in reducing greenhouse gases. Its production consists of the transesterification reaction of vegetable oil or animal fat with a short-chain alcohol, in the presence of a catalyst. On an industrial scale in Brazil, biodiesel is synthesized from soybean oil and methanol, under sodium methoxide catalysis. These 3 parameters do not favor the renewable character of biodiesel since; i) soy oil competes with a food; ii) methanol has a fossil origin which becomes meaningless when producing a renewable fuel; and iii) sodium methoxide is a homogeneous, non-reusable catalyst and needs to be removed with an aqueous solution in order to purify the biodiesel, generating a huge volume of effluents which, ultimately, also diminishes the environmental appeal of biodiesel as a biofuel. With all of this in mind, this work consisted of the study of the catalytic power of calcium oxide generated from the residues of shells from sururu, in order to produce biodiesel under the analysis of several parameters; i) ethanol and methanol as reagent alcohol; ii) neutral soybean oil and frying oil with 2 different acidity indices as starting oil; and iii) different reaction times in order to determine the kinetic behavior of this catalyst under each of these different parameters. Homogeneous catalysis was also performed in order to observe its behavior under extreme conditions and compare this behavior with heterogeneous catalysis. From studies of FTIR spectra, we verified the high catalytic efficiency of our oxide in the production of methyl biodiesel, both in neutral oil and in different acidic frying oils. This reaction success was attributed to the conversion of triglyceride to methyl esters above 95%. For the case of neutral oil, this efficiency was reached after 1 h of reaction and in the other cases after 3 to 4 h of reaction. The same success when observing the catalytic efficiency of converting soybean oil into ethylic biodiesel was also verified through the FTIR spectra, but this time without a calibration curve, which made a quantitative analysis impossible.