Composition of the gaseous products of pyrolysis of tobacco under inert and oxidative conditions

Abstract

Theoretical and modeling work on the process of cigarette combustion showed that in the puffing stage of the burning cycle thermal decomposition of cigarette components in the pre-heat zone of the cigarette may take place under oxygen-starving (in the inner part of the cigarette) versus oxygen-rich conditions (at the cigarette periphery). A companion paper [O. Senneca, R. Chirone, P. Salatino, L. Nappi, A. Nunziata, J. Anal. Appl. Pyrolysis, submitted for publication. [1]] addressed the pattern and the kinetics of pyrolysis under inert versus oxidative conditions of several tobaccos and reported profound differences as regards the number of reaction steps, the rate, the temperature ranges and the yield in solid and gaseous products. The present paper investigates the effects of inert versus oxidative conditions on the composition of the gas produced. The experimental work consists of non-isothermal thermogravimetric experiments in connection with MS analysis. Experiments have been carried out in a Netzsch TG Skimmer apparatus that minimizes secondary reactions of primary decomposition products in the gas phase. MS profiles have been analyzed to underline the differences in the evolution of gaseous products under inert versus oxidizing conditions. Three different tobaccos have been tested, including omogenized and Kentucky tobaccos. A first analysis regarded the temperature at which chemical species are released. Results showed that most species of interest in tobacco smoke, in particular nitrogen containing species, are produced over quite broad temperature ranges under inert conditions and over much more limited ranges under oxidizing conditions. A second comparison regarded the cumulative amount of the species released. Also with this respect large differences have been observed when tobaccos are heated under inert or oxidative conditions. Some species, like CO, CO 2, NO x and H 2O, appear to be strongly favoured by oxidative conditions. Other species such as amines, H 2, aldehydes, aromatics and poliaromatics are instead favoured by inert conditions. Acrolein, HCN, butanone and nicotine are favoured by inert conditions for omogenized tobaccos and by oxidative conditions for Kentucky tobacco.