Thermal degradation of tobacco in different atmospheres: kinetics analysis and chemical characterization of major and minor products

An extensive experimental campaign has been carried out on tobacco samples extracted from a commercially available Heated Tobacco Products (HTPs). The sample is a cast-leaf tobacco material, which includes not only the bio-polymers typical of lignocellulosic biomass but also some additives such as glycerol acting as an aerosol former during product operation. Heating temperatures in modern HTPs are typically kept below around 350°C and ignition/combustion is prevented, in order to limit or totally avoid the production of species, which are considered harmful for consumers’ health. However, a thorough understanding of the chemistry and the reaction paths of tobacco thermal degradation, which is the basis for an assessment of the potential health implications of tobacco emissions, is still missing. The aim of the present paper is to give insights on this topic. Experiments included tests in a thermogravimetric apparatus as well as in a fixed bed reactor with a sampling of gaseous, condensable (liquid) products, as well as degraded solid substrates. Isothermal and non-isothermal conditions have been tested, as well as different atmospheres (inert and oxidative). Gaseous and condensed products have been analyzed by a multitude of techniques to gain a complete picture of the evolution of both major and minor products. In particular, the following chemical species have been measured: CO, CO2, H2, CH4, NOx, Ethane, Ethene, Acetylene, Formaldehyde, Acetaldehyde, Nicotine, Naphthalene, Benzene, Pyrene, Chrysene, benzo[a]pyrene and benzo[a]anthracene. Data have been analyzed in order to: -Determine cast-leaf tobacco ignition conditions and thermochemical decomposition kinetics; -Establish a detailed description of cast-leaf tobacco thermochemical decomposition under inert and oxidative atmosphere; -Differentiate between the compounds formed by thermal degradation and those formed by oxidation.