Study of the effect of different catalysts in the decomposition of nicotine
Nicotine is the principal alkaloid component of tobacco, occurring throughout the plant (Nicotiana tabacum), and is the major inducer of tobacco dependence. It has not been classified as a carcinogen. Numerous studies concerning the thermal pyrolysis of nicotine indicate that nicotine is stable in inert atmosphere up to temperatures in excess of 600°C. In an oxidizing atmosphere (i.e., in air) nicotine begins to decompose around 300°C. Some of the pyrolysis and/or oxidation products of nicotine include myosmine, nicotyrine, nornicotine, and a variety of pyrrolidine ring-compounds, where most of them are considered carcinogenic. Zeolites and molecular sieves have been employed as additives in cigarettes in order to remove such dangerous products, but their effect on nicotine is not well known.
In this work, three catalysts with different physicochemical properties, and different concentrations, were employed: one without acidity (SBA-15), one with a low acidity (NaMCM-41) and another with high acidity (HMCM-41). When using SBA-15, similar results in air and N2 atmospheres were observed. A shift of the nicotine evolution peak at higher temperatures was observed when the SBA-15 concentration increased, probably because nicotine is adsorbed within its porous structure. IR spectra showed mainly nicotine in the gas evolved at all temperatures in N2 and also the presence of CO2 bands in air. The other two materials present a distinct behaviour, and a premature decomposition of the nicotine was observed at very low temperatures, both in air and N2 atmospheres. Two steps of desorption of nicotine are observed in both atmospheres. The IR spectra in air experiments show the presence of relatively intense bands not corresponding to nicotine. On another hand, a clear evolution of CO2 was observed in air at high temperatures as a consequence of the residue evolution. Consequently, it can be concluded that nicotine reacts in the presence of both MCM-41 type catalysts.
Acknowledgments: Financial support for this investigation has been provided by the Spanish “Secretaría de Estado de Investigación” del Ministerio de Economía y Competitividad (MAT2011-24991) and by the Generalitat Valenciana (PROMETEO/2012/015).