Produção e caracterização de biocombustíveis a partir da liquefação térmica de bagaço de cana-de-açúcar

Abstract

In the present thesis different routes of sugarcane bagasse liquefaction were studied for liquid fuels production. This waste from the sugar and alcohol industry was heated in a microprocessed Parr reactor under pressure (10 bar N2) at 300 ºC, for 30 min under 100 rpm of stirring using different solvents (water, anhydrous ethanol, hydrated ethanol, fusel oil). Except for fusel oil, waste catalysts based on calcium carbonate were used, which are derived from fishing residues from crab and mussel shells, which are widely available in maritime regions. The composition of the biocrudes was determined by gas chromatography coupled with mass spectrometry. There was difficulty in recovering the biocrude in the Hydrothermal Liquefaction (HTL) process, due to their great solubility in water, leading to a lower conversion (18%) in relation to reactions with ethanol (60%). It was also observed that the alkaline catalysts favored the formation of esters when hydrated ethanol was used as a solvent, reducing the concentrations of furans, sugars and aromatics, in relation to the process with anhydrous ethanol. With the use of fusel oil, which is a residue from the distillation of ethanol and is a mixture of higher alcohols, the liquefaction efficiency increased, because there was higher conversion into liquid products (91%). This result showed that fusel oil provided greater degradation of biopolymers, fragment stabilization and solubilization of polar compounds with high molar mass, regarding the ethanol. The presence of alcohols and esters of long alkyl chains (isoamyls) showed that there was simultaneous liquefaction, esterification and transesterification during this thermoconversion process, which can be considered a biocrude upgrading. A mixture of marine diesel with 5% of the biocrude (ethyl route) was prepared and it presented quality parameters within the permitted limits, showing the potential of this blend as an alternative marine fuel. It can be also tested for other fossil fuels. Coal/CaCO3 composites were obtained as residues in the catalyzed liquefactions, which were also characterized. These composites were converted into C-CaO catalysts, after thermal treatment, for use in the deoxygenation of vegetable oils for the production of drop-in biofuels. It was tested at low pressures of N2, leading to linear biohydrocarbons, with good yield (90% from oleic acid). The use of sugarcane bagasse, fusel oil and hydrated ethanol, in addition to residual catalysts, gives the work a great focus on circular economy and presents a proces with outstanding sustainability, suggesting low costs and potential for industrial application.