Catalysis of a nanometre solid super acid of SO42-/TiO2 on the thermal decomposition of ammonium nitrate

Abstract

Raw TiO2 nanoparticles were prepared using the hydrolysis of TiCl4. The nanoparticles were subjected to a surface treatment in diluted sulphuric acid and, subsequently, calcined at different temperatures. Then, a type of super solid acid (SO42-/TiO2) with particle sizes of 20~30 nm was fabricated. The catalysis of SO42-/TiO2 on the thermolysis of ammonium nitrate (AN) was probed using thermal analysis. For SO42-/TiO2 (AN doped with 3%SO42-/TiO2), the onset temperature decreased by 19°C and the peak temperature decreased by 15.8°C. For TiO2 (AN doped with 3%TiO2), the peak temperature decreased by only 0.5°C. Using the DSC-IR technology, the gas products of the decomposition of 3%SO42-/TiO2-doped AN were detected. We found that the products were mainly N2O (g) and a small amount of H2O (g), and that no NH3 (g) or HNO3 (g) was detected, which ascertained the decomposition reaction of NH4NO3→N2O(g)+H2O(g). In addition, the catalysis mechanism of SO42-/TiO2 on the AN decomposition was discussed in detail.