Efeito da temperatura e da adição de sais inorgânicos na pirólise analítica de resíduo de tabaco

Abstract

Biomass is an energetic alternative to provide fuels originated from renewable sources and with less pollutant characteristics. Currently, about 4000t/year of tobacco residue are generated in Brazil and fast pyrolysis is an option to convert biomass into fuels, like bio-oil, which can also be a source of high added value compounds. The present work aimed at characterizing tobacco residue, identifying the pyrolysis kinetic parameters of the material decomposition and studying the in uence of temperature and additives in the distribution of products generated in the pyrolytic reaction of this biomass. Thermogravimetric tests were performed with slow heating rates (5-25oC/min) and nitrogen inert atmosphere. Single reaction step and independent parallel reaction models were used to estimate the kinetic parameters of biomass decomposition. The single reaction step models presented activation energy values between 70,8 and 143,1kJ/mol; independent parallel reaction model indicated that the tobacco residue decomposition consists of six dierent reactions, with activation energies varying between 39,4 and 276,3kJ/mol. Next, analytical pyrolysis was applied to study the vapors produced in reactions of tobacco residue, either pure or added of 10% ZnCl2 and 10% MgCl2; at 400, 500, 600 and 700oC (20oC/ms) and helium inert atmosphere. Vapors with higher contents of acetic acid and furfural were identied for tobacco residue added of 10% MgCl2; and of nicotine and 4-penten-1-ol for pure residue; the pyrolysis of tobacco residue added of 10% MgCl2 provided vapors with the higher percentages of oxygenated compounds, ketones and aldehydes; vapors resulted from pyrolysis of residue added of 10% ZnCl2 presented the most expressive contents of hexadecane. Results indicated that the pyrolysis of tobacco residue, either pure or added of 10% of MgCl2 will generate bio-oils that could be considered source of compounds, and the pyrolytic reaction of the residue added of 10% of ZnCl2 a fuel oil with ignition quality. Finally, in order to evaluate the additive content eect in pyrolytic reactions at 500oC, analyses were performed for 5% and 20% of ZnCl2 and MgCl2 (20oC/ms, helium inert atmosphere). Higher ZnCl2 contents reduced nicotine and phenolic compounds percentages; while higher MgCl2 concentration reduced acetic acid, nicotine and phenolic compound contents, and increased furfural content; the percentages of oxygenated compounds and carboxylic acids were reduced and contents of ketones and aldehydes were increased when using higher MgCl2 concentration.