Produção biossustentável do biodiesel de sebo bovino com catalisador heterogêneo da casca de ovo

Abstract

The consumption of fossil fuels has been growing disproportionately due to intense global energy demand, reducing environmental quality. In this context, the search for sustainable energy alternatives has become a necessity. In Brazil, the main sources of clean and renewable energy are ethanol and biodiesel. Specifically for the production of biodiesel, it is necessary to use a catalyst to speed up the reaction and improve the efficiency of the process. Therefore, considering the use of catalysts, among heterogeneous catalysts, those based on calcium carbonate (CaCO3) or calcium oxide (CaO) have great potential for the transesterification reaction. In this sense, this work intends to analyze the feasibility of producing biodiesel from beef tallow through methyl transesterification and heterogeneous catalysis with calcium oxide synthesized from the calcination of chicken eggshells, in addition to verifying the physicochemical properties of the catalyst and ester produced. Among the heterogeneous catalysts, the greatest potential in the transesterification reaction are those based on CaO or CaCO3, which transforms into CaO when calcined. In the methodology, chicken egg shells, provided by a local bakery, were first dried in an oven at 120°C, crushed in a blender and calcined in a muffle oven at 850°C for 4h. The obtained catalyst was characterized by the following analyses: X-ray diffraction (XRD); Differential and thermogravimetric scanning calorimetry (DSC/TG); Scanning electron microscopy (SEM). Biodiesel was produced with magnetic stirring in a reflux system and water bath for 1 to 4h at a temperature of 65°C. To do so, 50g of tallow was used, with the stoichiometric ratios of tallow: alcohol of 1:12, 1:9, 1:15. 1:20, and amount of catalyst of 3%, 8% and 20% in relation to the amount of tallow. As a result, problems were observed with the parameters analyzed for raw material A, with a high acidity level and density. Raw material B met the required parameters and biodiesel had results within the legislation required according to the ANP. In the catalyst, XRD analysis showed a crystalline structure similar to CaO, confirming the conversion by calcination. The SEM demonstrated that there was a change in the crystalline structures of the fresh eggshell compared to the catalyst. TG analysis proved that temperatures above 800°C can be used to obtain catalysts, as they guarantee the production of CaO in its purest form. The condition with 8% catalyst and tallow wet: alcohol ratio 1:20 was the one with the best conversion of triglycerides into esters, despite the difficulties related to the high acidity of the raw material. In conclusion, it is possible to use chicken eggshells as an alternative to produce a catalyst used to produce beef tallow biodiesel through methyl transesterification. Therefore, using beef tallow and chicken eggshells to produce biodiesel removed two wastes from the environment that would normally be discarded irregularly, and used them to produce a less polluting and renewable fuel.