Effect of SBA-15 on the thermal decomposition of NNK and NNN tobacco specific nitrosamines
Tobacco specific nitrosamines (TSNAs) are among the most carcinogenic compounds present both in tobacco and tobacco smoke, N-nitrosonornicotine (NNN), N-nitrosoanabasine (NAB), N-nitrosoanatabine (NAT) and 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK) being the most abundant. The Knowledge of their thermal behaviour and decomposition products, as well as the effect of potential catalysts for reducing their concentration is of great interest. Thus, the present study presents preliminary results on the thermal degradation of two TSNA (i.e.: NNK and NNN) under different conditions, and in the presence of SBA-15 catalysts. NNK and NNN with and without catalyst were thermally treated under two atmospheres at different temperatures using a pyrolizer (Py/EGA-GC/MS) online with a gas chromatographer coupled with mass selective detector. Flash pyrolysis was run under He atmosphere, at 300, 400 and 500 °C. Flash pyrolysis under synthetic air oxidative atmosphere was performed at 325, 375, 425 and °C. A SBA-15 mesoporous catalyst, synthetized in our laboratory, with fibre like morphology, was used. SBA-15 was characterized by N2 adsorption isotherms, scanning electron micrographs (SEM) and transmission electron micrographs (TEM) and X-ray diffraction. The presence of the catalyst under inert atmosphere promotes the decomposition of NNK and NNN and modifies the product distribution generating, in the case of NNK, myosmine, nicotyrine as the major degradation compounds, as compared with 4-Hydroxyphenyl acetonitrile in absence of the catalyst. Under oxidative atmosphere the catalyst also accelerates the decomposition of both Nitrosamines. Noting that in the case of NNN, SBA-15 favours the formation of lower molecular weight compounds.