Espectroscopia por FTIR de variedades híbridas de bagaço de cana-de-açucar pré-tratados para produção de etanol celulósico

Abstract

Energy is indispensable for the economy and development of the Brazilian State. The imminent fossil fuels scarcity and current environmental concerns has attracted a new race for renewable energy sources. In Brazil, the use of first generation ethanol is produced by sugarcane juice fermentation and the second ethanol generation or cellulosic ethanol is produced from sugarcane bagasse. This residue is burned normaly in the place where is produced for energy generation in the juice extraction process, that can to be utilized for celulosic ethanol. In this context, the work present results based in use of optical Fourier transform infrared spectroscopy (FTIR) to characterize fragmentation process of sugarcane bagasse for ethanol cellulosic production and to otmize this process as well as to understand FTIR spectroscopy theory and experimentation. This technique was utilized to characterize pretreated bagass from five hybrid sugarcane varieties an to detect difference amont these varieties for ethanol production. Samples were divides as follow: (a) bagasse in nature; (b) bagasse extracted; (c) acid hidrolysis; (d) alkaline hidrolysis. 20 samples were characterized. In (a) samplas were only ground with objective to identify bagass optical characteristics no treatment. In (b) bagasse was pretreated with water and ethanol to extract non-structural compounds. In (c) bagasse suffered acid hydrolisis with sulfuric acid to disrupt bagasse lignocellulosic structure and to remove content hemicellulose and step (d) bagasse suffered hidrolisis alkaline with sodium hidroxide to remove most possible content of lignin. In molecular vibrations from in nature bagasse were obtained bands among 1000 and 890 cm-1 that identify cellulose charateristics, 1200 and 1000 cm-1 for hemicellulose and cellulose, 1247 cm-1 for hemicellulose and lignin, 1430 and 1300 cm-1 with superposition of cellulose, hemicellulose and lignin bands, among 1610 and 1460 cm-1 for lignin, 1735 cm-1 for hemicellulose, 2920 and 2850 cm-1 for cellulose and 3800 and 3000 cm-1 for crystalline cellulose characteristics. In the extraction process with water and ethanol were not observed difference. Acid hidrolysis was effective to disrupt lignocellulisic structure and to remove most part of hemicellulose, determined by decrease or disappearance of some bands. Alkaline hidrolysis removed part of lignin and was responsible by changes in the ligninocellusolic structure, provened by some bands displacements. It was concluded that pretreat sugarcane bagasse with acid and alkaline hidrolisis have great conditions of utilization to enzimatic hidrolisis and fermentation to ethanol and that bagasse varieties respond similarly to pretreatment.