Estudo analítico, térmico e energético do pinhão manso (Jatropha Curcas l.) como matéria-prima para a produção de biocombustíveis

Abstract

The Jatropha curcas L. is a vegetable species that supplies great amount of oil, but due to its toxicity cannot be used to feed human beings. It is a promising alternative for Biodiesel production. This Thesis had the purpose of perform analytic, thermal and energy studies for the oil extracted from oleaginous species Jatropha curcas L., cultivated in the State of Amazonas. The study was also done for byproducts such as fruit peels, seed peels and the cake originated by biofuel productive chain. To reach the proposed objective, the experimental activities were started with the sampling of the whole fruits in a plantation located in Itacoatiara city-Amazonas. Six independent samplings were done in different months and all the samples were submitted to physical characterization to evaluate size and weight for all parts of the fruit. The process to obtain the oil was done by two methods: mechanical extraction and chemical extraction (Soxhlet system). The chemical extraction was performed for all available samples and the best efficiency was the 50.21%, although all the extractions have presented good results (43-48%). The mechanical process was just performed for the 2010 crop presenting a satisfactory efficiency (33.14%). Then, the oil extracted by the two processes was characterized by several physical-chemical parameters. The oxidative stability by Rancimat was measured for the oils and the result was around 12 hours, this value is considered satisfactory when compared with other species. The fatty acid profile was analyzed by gas chromatography, which indicated the presence of higher concentrations of oleic and linoleic acids. The palmitic, stearic, arachidic and palmitoleic acids were also detected, however in smaller concentrations. The evaluation for thermal and energy potential was done for the oil and byproducts using TG/DTA, immediate analysis and superior heat power techniques. The results of thermal analysis for the oils obtained by chemical and mechanical extraction indicated thermal stability temperature about 180 and 217°C, respectively. Energy evaluation for byproducts was done by immediate analysis and high values for volatile materials were found (65-78%). These values characterize a fuel that can be easy and quickly burned during the combustion process. The results of PCS for the obtained oils presented high values (34-39 MJ/kg), which are close to the ones measured for diesel. For the byproducts, the results were between 17 and 21 MJ/kg, close and even superiors to the literature values for other agricultural residues showing, therefore, great applicability for use in energy generation processes. Finally, reactions with the Jatropha curcas L. oil were made to obtain biofuels through the methylic and ethylic transesterification and thermal cracking. The results for transesterification process were excellent, with efficiency above 90%, however, the physical-chemical evaluation showed that the methylic Biodiesel was the only one in conformity with the Resolution 14/2011 from ANP. A satisfactory efficiency of 75% was obtained for bio-oil.