Reaction Kinetics and Process Optimization for Nitration of 2-Methyl-4, 6-Dihydroxy-Pyrimidine

摘要

1,1-Diamino-2,2-dinitroethene (FOX-7) is a thermally stable insensitive high explosive. Fox-7 is synthesised by nitration of 2-methyl-4,6-dihydroxy- pyrimidine (MDP). Nitration of MDP is a low temperature and highly exothermic reaction. Adiabatic rise in temperature of this nitration reaction is very high (>220℃) which indicates that the conduct of reactions at lowest possible optimum temperature is safer and favourable. In order to optimise the reaction time without compromising yield, the reaction kinetics have been studied at three different temperatures (5℃, 15℃ and 25℃) using differential method. The effect of temperature on yield(%) of FOX-7 has also been studied at two more additional temperatures, 35℃ & 42℃. Since the nitration of MDP is sensitive to temperature, rate of reaction was studied at fixed temperature with the variation of time keeping all the other parameters constant In the present studies, it is found that optimum temperature of nitration is 15℃ and rate of reaction follows pseudo second order with a rate constant 0.0338 (min-1) (concentration-1) . The reaction time evaluated for 85% conversion is around 1.8 hrs at 15℃ based on the kinetics, which resembles to calorimetric studies too. Activation energy of MDP nitration is found to be 42kJ/mole, using reaction kinetic data based on temperature dependent rate equation derived from the Arrhenius's law. Heat generation rate increases with the increase of reaction temperature.