Thermolysis mechanism of chromium nitrate nonahydrate and computerized modeling of intermediate products

• Published in: Journal of thermal analysis and calorimetry Vol. 114; no. 3; pp. 1021 - 1027
• Main Authors: Melnikov, P., Nascimento, V. A., Arkhangelsky, I. V., Zanoni Consolo, L. Z., de Oliveira, L. C. S.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-12-2013; Springer
• Subjects: Analytical Chemistry; Calorimetry; Chemistry; Chemistry and Materials Science; Chromium dioxide; Diffraction; Infrared spectroscopy; Inorganic Chemistry; Measurement Science and Instrumentation; Physical Chemistry; Polymer Sciences; Pyrolysis; X-rays; Thermal decomposition; Computer modeling; Chromium nitrate
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-013-3106-3

Thermal decomposition of chromium nitrate nonahydrate was studied by thermal analysis, differential scanning calorimetry, infrared spectroscopy, and high temperature X-ray diffraction, so that mass losses were related to the exactly coincident endothermic effects and vibrational energy levels of the evolved gases. The thermal decomposition of chromium nitrate is a complex process, which begins with the simultaneous dehydration and concurrent condensation of 4 mol of the initial monomer Cr(NO
3
)
3
·9H
2
O. Soon after that, the resulting product Cr
4
N
12
O
36
·31H
2
O gradually loses water and azeotrope HNO
3
 + H
2
O, and is transformed into tetrameric oxynitrate Cr
4
N
4
O
16
. At higher temperatures, the tetramer loses N
2
O
3
and O
2
and a simultaneous oxidation of Cr(III) to Cr(IV) occurs. The resulting composition at this stage is chromium dioxide dimer Cr
4
O
8
. Finally, at 447 
°
C the unstable dimer loses oxygen and is transformed into 2Cr
2
O
3
. The models of intermediate amorphous compounds represent a reasonably good approximation to the real structures and a proper interpretation of experimental data.