Kinetic Study of Hexamine Degradation in Acetic Acid and its Effect on the Efficiency and Purity of HMX in Beckman Process

Dissolved hexamine in acetic acid is used as precursor in production of HMX explosive by Beckmann procedure. But, the gradual degradation of hexamine is occurred in acidic media, leading to decrease of purity and efficiency of HMX. In this research, the kinetic of degradation reaction of hexamine is studied in acetic acid media. The concentration of formaldehyde as product of degradation reaction of hexamine is measured by spectrophotometric method. The pseudo first order constants of degradation reaction are determined at 25, 35 and 45 oC. The activation energy of degradation reaction of hexamine is obtained 32.2 kJ/mol by Arrhenius equation. The obtained results showed degradation 5% for dissolved hexamine in acetic acid at conditions of initial concentration of 38% W/W, time of 34 h and temperature of 45 oC. The efficiency of HMX production in Beckman procedure is obtained as 49.0 and 31.5%, respectively, for fresh and aged hexamine solution after 30 days. The impurity of RDX as a by-product is increased from 11 to 35% with aging of hexamine solution.