## 4 Conclusions  
This study, developed in the absence and presence of three catalysts, has made it possible to highlighting a series of conclusions that are shown below:  
* According to the TG-FTIR analysis of NNN, two main processes of weight loss can be observed. The peaks appears 10 \({}^{\circ}\)C before when running the analysis under oxidizing atmosphere, where the main gases analyzed by FTIR show the characteristic band of C=C and the presence of CO\({}_{2}\). * The presence of the three catalysts has produced modifications in the temperature and intensity of the observed processes, mainly under oxidizing conditions, where the three materials present a third process of weight loss due to the oxidation of the residue. The three materials, mainly MCM-41, show increased IR signals corresponding to CO and CO\({}_{2}\) at temperatures in the range of the third process. * NNN decomposes at lower temperatures under an oxidizing atmosphere than under an inert atmosphere in the EGA equipment. During the NNN pyrolysis under the inert atmosphere, the main compounds obtained were 3-pyridinecarbonitrile, myosmine and nonnicotine. Meanwhile, under the oxidizing atmosphere, the main compounds obtained are 3-pyridinecarbonitrile, myosmine and 5,6-dimethyl-3H-pyrrolo [2,3-b] pyridine, along with CO\({}_{2}\) and water as products of the oxidative degradation of different organic molecules. * The three catalysts reduce the contribution of the NNN to the total area for both atmospheres in the flash pyrolysis of NNN, especially under inert atmosphere. SBA-15p and SBA-15f highly reduce the contribution of NNN to the total area, especially under the inert atmosphere. However, MCM-41 shows a smaller total area than both SBA-15, \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**SBA-15f**} & \multicolumn{2}{c}{**SBA-15p**} & \multicolumn{2}{c}{**MCM-41**} \\  & & He & air & He & air & He & air \\ \hline
5 & _Hydrogen cyanide_ & - & \(\uparrow\) & - & \(\uparrow\) & - & \(\uparrow\) \\
6 & _Acetaldehyde_ & - & \(\downarrow\) & - & \(\uparrow\) & - & \(\uparrow\) \\
7 & _Formaldehyde_ & - & \(\downarrow\) & - & \(\downarrow\) & - & \(\downarrow\) \\
9 & _Propaneitrile_ & \(\downarrow\) & - & \(\downarrow\) & - & \(\downarrow\) & - \\
10 & _Pyridine_ & \(\downarrow\) & - & \(\uparrow\) & - & \(\uparrow\) & - \\
11 & _3-ethenyl-pyridine_ & \(\downarrow\) & \(\downarrow\) & \(\uparrow\) & \(\uparrow\) & \(\uparrow\) & \(\downarrow\) \\
24 & _Nicotine_ & \(\uparrow\) & - & \(\uparrow\) & - & \(\uparrow\) & - \\
35 & _NNN_ & \(\downarrow\) & \(\downarrow\) & \(\downarrow\) & \(\downarrow\) & \(\downarrow\) & \(\downarrow\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Toxic compounds present in the gas generated in the pyrolysis of NNN under both atmospheres. as well as a lower presence of decomposition products and NNN in the chromatograms, in good agreement with the higher residue observed in the TGA experiments. * The three materials studied strongly modify the product distribution of the gases generated during the pyrolysis of NNN, especially under the oxidizing atmosphere, with 3-pyridinecarbonitrile and myosmine being the two major compounds. For example, myosmine contribution is reduced in the air atmosphere when using SBA-15p and MCM-41. This type of behavior must be due to the higher external specific surface area, pore size and pore volume, resulting in a greater accessibility of the NNN molecule to the porosity of this material. Although the pore size of MCM-41 is significantly smaller, as well as the external area, its highest total area and, mainly, its acidity, may justify its good behavior, better than that of the SBA-15\(f\). * Nevertheless, SBA-15f is the catalysts yielding the largest reduction in toxic compounds highlighted from the Hoffman list and generated in the pyrolysis of NNN. Conceptualization, A.M., M.I.B. and J.A. ; Methodology, A.M., M.I.B. and J.A. ; Validation, A.M., M.I.B. and J.A. ; Investigation, J.A. ; Resources, A.M.; Data Curation, A.M., M.I.B., D.B. and J.A.