A comprehensive study on the thermal reaction mechanism, products and kinetic characteristics of cut tobacco

Abstract

During smoking, the cut tobacco undergoes a series of thermal decomposition and secondary reactions when heated, resulting in the production of harmful substances such as nicotine, CO and furfural, which caused various diseases. Therefore, to elucidate the decomposition and transformation pathways of cut tobacco components and investigate the formation of harmful substances, it is necessary to conduct in-depth research on the thermal reaction mechanism of cut tobacco. To this end, this study employed TG-FTIR to analyze the thermal reaction process and product distribution with different oxygen concentrations. Additionally, the overall pyrolysis reaction of cut tobacco was divided into five independent parallel pyrolysis reactions according to the DTG pattern. The kinetic analysis of these five reactions was carried out using the iso-conversional method. The compensation effect was applied to achieve the separation of the pre-exponential factor A(α) and the reaction mechanism function f(α). The results indicated that the cut tobacco pyrolysis could be segmented into five stages. The major weight loss occurred in the second, third and fourth stages (approximately 222–600 °C), where most of the pyrolysis products were generated, including small molecular gases (such as H₂O, CO, CO₂ and alkanes) and organic components (including alcohols, phenols, aromatic compounds, as well as carbonyl groups like aldehydes, ketones and acids). The involvement of oxygen became effective in the fourth stage (around 355–600 °C) of cut tobacco pyrolysis, where the combustion of char took place, producing a large amount of CO₂. The yields of carbonyl compounds, alcohols and phenols decreased in this stage. The kinetic investigation found that the activation energies of lignin pyrolysis showed the most significant changes in activation energy. This study elucidated the mechanisms of cut tobacco pyrolysis and the releasing of the products, providing theoretical references for a deeper understanding of the thermal reaction characteristics and data support for the thermal reaction equation of a comprehensive cigarette numerical simulation.