Analysis of Pyrolysis Characteristics and Kinetics of Cigar Tobacco and Flue-Cured Tobacco by TG-FTIR

Investigation of the detailed pyrolysis characteristics of tobacco raw materials is important for the understanding of product design and consumption. In this work, pyrolysis characteristics and kinetic models of cigar filler tobacco (CFT), cigar wrapper tobacco (CWT), and flue-cured tobacco (FCT) were investigated by using a thermogravimetric analyzer coupled with Fourier-transform infrared spectroscopy (TG-FTIR). The pyrolysis of different tobacco samples could be divided into four stages based on the derivative thermogravimetric analysis (DTG) curves. Flue-cured tobacco underwent a marked decomposition process at lower temperatures (about 200 °C), while the thermal decomposition of cigar tobacco occurs at higher temperatures. During the pyrolysis process, evolved gases including H₂O, CO₂, CH₄, CO, carbonyls, alcohols, phenols and aromatic compounds were detected by FTIR. CWT released more CO₂ than CFT, while the amount of CO₂, CH₄, CO and aromatic compounds released by flue-cured tobacco was lower than that of cigar tobacco. The pyrolysis kinetics of tobacco leaves were further analyzed and compared through the isoconversional FWO (Flynn-Wall-Ozawa) and KAS (Kissinger-Akahira-Sunose) methods. The activation energy of FCT (from 100.1 kJ mol⁻¹ to 192.1 kJ mol⁻¹) was lower than that of CFT (from 207.36 kJ mol⁻¹ to 319.28 kJ mol⁻¹) and CWT (from 160.40 kJ mol⁻¹ to 260.45 kJ mol⁻¹). The thermal decomposition kinetics of different tobaccos were analyzed by Málek and Coats-Redfern methods.