Thermal decomposition processes of a reconstituted cast-leaf tobacco: fate of nitrogen and carbon

Thermal decomposition of a reconstituted cast-leaf tobacco used in heated tobacco products (HTPs) was investigated. Experiments were carried out in a small-scale fixed-bed reactor, under both inert (N2) and oxidative (air) atmospheres, at different final temperatures (250–500 °C) and under isothermal conditions. This study focuses on determining the fate of nitrogen and carbon present in tobacco upon heat treatment. Results show that in both oxidative and inert atmospheres, NOx formation is limited; consequently, only a small fraction of tobacco nitrogen is released into the gas phase as NOx. However, this does not exclude the presence of other volatile nitrogen-containing species in the gas phase. Overall, the nitrogen originally present in tobacco likely remains predominantly in the solid phase under inert atmosphere, whereas under oxidative conditions most of the detected nitrogen is associated with the oil fraction. Regarding the carbon balance, the results show that, under inert conditions, carbon is mainly retained in the solid product, particularly at low temperatures. In contrast, under oxidative conditions, carbon is predominantly converted into gaseous species, mainly CO and CO2.