Energetic bimetallic complexes as catalysts affect the thermal decomposition of ammonium perchlorate

Two bimetallic complexes of 4-hydroxy-3,5-dinitropyrazole, [K2Mn(DNPO)2(H2O)4]n·2H2O (BMEP-1) and [K2Zn(DNPO)2(H2O)6]n (BMEP-2), were synthesized and characterized by IR spectroscopy and elemental analysis. The crystal structures of BMEP-1 and BMEP-2 were determined by single-crystal X-ray diffraction. It is noteworthy that these complexes presented different metal-organic frameworks. The thermal behaviors of BMEP-1 and BMEP-2 were investigated by differential scanning calorimetry and thermogravimetric analysis measurements. These bimetallic complexes exhibited high thermal stability (348.0 °C and 331.0 °C) due to their large coordination bonds and three-dimensional interconnected structure. The catalytic performances of BMEP-1 and BMEP-2 on the thermal decomposition of ammonium perchlorate were investigated by TGA-DSC, TGA-FTIR, and non-isothermal kinetic analyses. The results showed that BMEP-1 and BMEP-2 exhibited excellent catalytic performance in the thermal decomposition of ammonium perchlorate. Notably, there was only a single exothermic peak at 302.6 °C and 318.6 °C, and the activation energy values of ammonium perchlorate decreased to 123.88 kJ mol-1 and 128.43 kJ mol-1, respectively. TGA-FTIR results showed that BMEP-1 and BMEP-2, as effective components of catalysis, will promote the production of H2O, N2O, NO2, and HCl in advance, during the thermal decomposition of ammonium perchlorate. BMEP-1 and BMEP-2 are expected to be two candidate additives for the catalytic decomposition of ammonium perchlorate in composite solid propellants.