|
Abstract
|
Different salts of 1,1′-dimethyl-4,4′-bipyridinium which known as methyl viologen compounds (MVX2) (where X= iodide (I‾, MVI2), perchlorate (ClO4‾, MVC2) and tetraphenylborate anion (BPh4‾, MVT2)) were prepared and characterized using 1H NMR, 13C NMR, elemental analysis and mass spectroscopy. The impact of these viologen salts on the thermal decomposition of ammonium perchlorate was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and mass spectroscopy. The obtained results revealed that the high-temperature decomposition (HTD) temperature of MVX2:AP mixtures (5:100 (w/w)) significantly decreases by 121 ◦C, 151 ◦C and 112 ◦C compared to pure AP in MVC2, MCI2 and MVT2, respectively. Moreover, the apparent released heat of AP decomposition in these mixtures grows up from 574.2 J g−1 for the pure AP to 2108, 1965 and 1564 J g−1 for MVC2, MCI2 and MVT2, respectively. Furthermore, the calculation of the kinetic parameters confirms that the activation energy of HTD of AP was significantly decreased from 142.9 to 124.9, 138.9 and 131.2 KJ mol−1, upon mixing with MVC2, MVI2 and MVT2 respectively. The rate constant of AP decomposition at the peak temperatures of these mixtures was higher than that at the peak temperature of pure AP. The evolved gas analysis using mass spectrometry shows that the decomposition of pure AP mainly results in ClO3, ClO2, HClO4, ClO, Cl2, HCl, N2O and O2, while the major gaseous products of the 5:100 (w/w) mixture of MVX2 salts with AP were detected as N2, NO, N2O, O2, Cl2, ClO, ClO2, ClO3, HClO4, HCl and 4, 4′-Bipyridine (Bpy). The amounts of Bpy in decomposition products of AP/MVX2 mixtures follow the order of MVC2>MVI2>MVT2, which surprisingly is in accordance with the catalytic activity of these compounds.
|