Evolved gas analyses (TG/DTA–MS and TG–FTIR) on dehydration and pyrolysis of magnesium nitrate hexahydrate in air and nitrogen

Thermally evolved gases from [Mg(H2O)6](NO3)2 released in flowing air and nitrogen atmosphere have been analyzed and monitored by simultaneous thermogravimetry and differential thermal analysis coupled online with mass spectrometer (TG/DTA–MS) and with FTIR spectroscopic gas cell (TG–FTIR) up to 700 °C.Both in air and nitrogen the mass spectrometry (TG/DTA–MS) definitely proved parallel evolution of O2 (m/z = 32, 16) and NO2 (m/z = 30, 46, 47, 48) between 300 and 500 °C. The m/z = 30 ion fragment with highest intensity among the fragments of nitrogen oxides might suggest parallel evolution of NO, anyhow, according to NIST reference spectra, m/z = 30 is also the most intense fragment of NO2 itself. The intense generation of oxygen resulted in parallel occurrence of m/z = 44 and 45 fragments indicating N2O or rather CO2 originated from reaction of nascent oxygen with the surrounding furnace. Whilst, the TG–FTIR spectroscopy showed evolution of NO2 indicated by two PR bands positioned at 1616 and 2911 cm−1, but no vibration bands of NO and N2O gases could be detected, at all. At greater initial loads, IR absorption bands of HNO3 vapour centred at 885, 1314, 1708, and 3566 cm−1 have been observed.