Catalysis of HMX Decomposition and Combustion: Defect Chemistry Approach

The influence of nanosized oxides of Ti, Al, Fe, and Si on the HMX thermolysis and combustion is reported. The following order of their catalytic efficiency in HMX thermolysis was obtained: TiO₂>Fe₂O₃≈Al₂O₃>SiO₂. The catalytic performance was analyzed and the key factors were shown to be specific surface area, content, and the acid/base properties of the metal oxide surface. Results reveal the burning rate increases and the pressure exponent decreases considerably by the addition of exceptionally nano-TiO₂.Since in catalysis reactions occur at interfaces, point defects in the catalyst material are to be considered in the interfacial catalysis mechanism. Intrinsic and extrinsic point defects in TiO₂ are discussed. The presence of acidic or basic surface groups influences the space charges and hence the catalytic efficiency.Based on the experimental results, the physicochemical model (scenario) of the decomposition and combustion of the HMX/TiO₂ mixtures is elaborated.